diff options
Diffstat (limited to 'Documentation/admin-guide/blockdev')
| -rw-r--r-- | Documentation/admin-guide/blockdev/drbd/figures.rst | 4 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/drbd/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/drbd/peer-states-8.dot (renamed from Documentation/admin-guide/blockdev/drbd/node-states-8.dot) | 5 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/floppy.rst | 6 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/index.rst | 6 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/nbd.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/paride.rst | 388 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/ramdisk.rst | 66 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/zram.rst | 192 |
9 files changed, 260 insertions, 411 deletions
diff --git a/Documentation/admin-guide/blockdev/drbd/figures.rst b/Documentation/admin-guide/blockdev/drbd/figures.rst index bd9a4901fe46..9f73253ea353 100644 --- a/Documentation/admin-guide/blockdev/drbd/figures.rst +++ b/Documentation/admin-guide/blockdev/drbd/figures.rst @@ -25,6 +25,6 @@ Sub graphs of DRBD's state transitions :alt: disk-states-8.dot :align: center -.. kernel-figure:: node-states-8.dot - :alt: node-states-8.dot +.. kernel-figure:: peer-states-8.dot + :alt: peer-states-8.dot :align: center diff --git a/Documentation/admin-guide/blockdev/drbd/index.rst b/Documentation/admin-guide/blockdev/drbd/index.rst index 68ecd5c113e9..561fd1e35917 100644 --- a/Documentation/admin-guide/blockdev/drbd/index.rst +++ b/Documentation/admin-guide/blockdev/drbd/index.rst @@ -10,7 +10,7 @@ Description clusters and in this context, is a "drop-in" replacement for shared storage. Simplistically, you could see it as a network RAID 1. - Please visit http://www.drbd.org to find out more. + Please visit https://www.drbd.org to find out more. .. toctree:: :maxdepth: 1 diff --git a/Documentation/admin-guide/blockdev/drbd/node-states-8.dot b/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot index bfa54e1f8016..6dc3954954d6 100644 --- a/Documentation/admin-guide/blockdev/drbd/node-states-8.dot +++ b/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot @@ -1,8 +1,3 @@ -digraph node_states { - Secondary -> Primary [ label = "ioctl_set_state()" ] - Primary -> Secondary [ label = "ioctl_set_state()" ] -} - digraph peer_states { Secondary -> Primary [ label = "recv state packet" ] Primary -> Secondary [ label = "recv state packet" ] diff --git a/Documentation/admin-guide/blockdev/floppy.rst b/Documentation/admin-guide/blockdev/floppy.rst index 4a8f31cf4139..0328438ebe2c 100644 --- a/Documentation/admin-guide/blockdev/floppy.rst +++ b/Documentation/admin-guide/blockdev/floppy.rst @@ -6,7 +6,7 @@ FAQ list: ========= A FAQ list may be found in the fdutils package (see below), and also -at <http://fdutils.linux.lu/faq.html>. +at <https://fdutils.linux.lu/faq.html>. LILO configuration options (Thinkpad users, read this) @@ -220,11 +220,11 @@ It also contains additional documentation about the floppy driver. The latest version can be found at fdutils homepage: - http://fdutils.linux.lu + https://fdutils.linux.lu The fdutils releases can be found at: - http://fdutils.linux.lu/download.html + https://fdutils.linux.lu/download.html http://www.tux.org/pub/knaff/fdutils/ diff --git a/Documentation/admin-guide/blockdev/index.rst b/Documentation/admin-guide/blockdev/index.rst index b903cf152091..957ccf617797 100644 --- a/Documentation/admin-guide/blockdev/index.rst +++ b/Documentation/admin-guide/blockdev/index.rst @@ -1,8 +1,8 @@ .. SPDX-License-Identifier: GPL-2.0 -=========================== -The Linux RapidIO Subsystem -=========================== +============= +Block Devices +============= .. toctree:: :maxdepth: 1 diff --git a/Documentation/admin-guide/blockdev/nbd.rst b/Documentation/admin-guide/blockdev/nbd.rst index d78dfe559dcf..faf2ac4b1509 100644 --- a/Documentation/admin-guide/blockdev/nbd.rst +++ b/Documentation/admin-guide/blockdev/nbd.rst @@ -14,7 +14,7 @@ to borrow disk space from another computer. Unlike NFS, it is possible to put any filesystem on it, etc. For more information, or to download the nbd-client and nbd-server -tools, go to http://nbd.sf.net/. +tools, go to https://github.com/NetworkBlockDevice/nbd. The nbd kernel module need only be installed on the client system, as the nbd-server is completely in userspace. In fact, diff --git a/Documentation/admin-guide/blockdev/paride.rst b/Documentation/admin-guide/blockdev/paride.rst index 87b4278bf314..e85ad37cc0e5 100644 --- a/Documentation/admin-guide/blockdev/paride.rst +++ b/Documentation/admin-guide/blockdev/paride.rst @@ -3,6 +3,7 @@ Linux and parallel port IDE devices =================================== PARIDE v1.03 (c) 1997-8 Grant Guenther <grant@torque.net> +PATA_PARPORT (c) 2023 Ondrej Zary 1. Introduction =============== @@ -51,27 +52,15 @@ parallel port IDE subsystem, including: as well as most of the clone and no-name products on the market. -To support such a wide range of devices, PARIDE, the parallel port IDE -subsystem, is actually structured in three parts. There is a base -paride module which provides a registry and some common methods for -accessing the parallel ports. The second component is a set of -high-level drivers for each of the different types of supported devices: +To support such a wide range of devices, pata_parport is actually structured +in two parts. There is a base pata_parport module which provides an interface +to kernel libata subsystem, registry and some common methods for accessing +the parallel ports. - === ============= - pd IDE disk - pcd ATAPI CD-ROM - pf ATAPI disk - pt ATAPI tape - pg ATAPI generic - === ============= - -(Currently, the pg driver is only used with CD-R drives). - -The high-level drivers function according to the relevant standards. -The third component of PARIDE is a set of low-level protocol drivers -for each of the parallel port IDE adapter chips. Thanks to the interest -and encouragement of Linux users from many parts of the world, -support is available for almost all known adapter protocols: +The second component is a set of low-level protocol drivers for each of the +parallel port IDE adapter chips. Thanks to the interest and encouragement of +Linux users from many parts of the world, support is available for almost all +known adapter protocols: ==== ====================================== ==== aten ATEN EH-100 (HK) @@ -91,251 +80,87 @@ support is available for almost all known adapter protocols: ==== ====================================== ==== -2. Using the PARIDE subsystem -============================= +2. Using pata_parport subsystem +=============================== While configuring the Linux kernel, you may choose either to build -the PARIDE drivers into your kernel, or to build them as modules. +the pata_parport drivers into your kernel, or to build them as modules. In either case, you will need to select "Parallel port IDE device support" -as well as at least one of the high-level drivers and at least one -of the parallel port communication protocols. If you do not know -what kind of parallel port adapter is used in your drive, you could -begin by checking the file names and any text files on your DOS +and at least one of the parallel port communication protocols. +If you do not know what kind of parallel port adapter is used in your drive, +you could begin by checking the file names and any text files on your DOS installation floppy. Alternatively, you can look at the markings on the adapter chip itself. That's usually sufficient to identify the correct device. -You can actually select all the protocol modules, and allow the PARIDE +You can actually select all the protocol modules, and allow the pata_parport subsystem to try them all for you. For the "brand-name" products listed above, here are the protocol and high-level drivers that you would use: - ================ ============ ====== ======== - Manufacturer Model Driver Protocol - ================ ============ ====== ======== - MicroSolutions CD-ROM pcd bpck - MicroSolutions PD drive pf bpck - MicroSolutions hard-drive pd bpck - MicroSolutions 8000t tape pt bpck - SyQuest EZ, SparQ pd epat - Imation Superdisk pf epat - Maxell Superdisk pf friq - Avatar Shark pd epat - FreeCom CD-ROM pcd frpw - Hewlett-Packard 5GB Tape pt epat - Hewlett-Packard 7200e (CD) pcd epat - Hewlett-Packard 7200e (CD-R) pg epat - ================ ============ ====== ======== - -2.1 Configuring built-in drivers ---------------------------------- - -We recommend that you get to know how the drivers work and how to -configure them as loadable modules, before attempting to compile a -kernel with the drivers built-in. - -If you built all of your PARIDE support directly into your kernel, -and you have just a single parallel port IDE device, your kernel should -locate it automatically for you. If you have more than one device, -you may need to give some command line options to your bootloader -(eg: LILO), how to do that is beyond the scope of this document. - -The high-level drivers accept a number of command line parameters, all -of which are documented in the source files in linux/drivers/block/paride. -By default, each driver will automatically try all parallel ports it -can find, and all protocol types that have been installed, until it finds -a parallel port IDE adapter. Once it finds one, the probe stops. So, -if you have more than one device, you will need to tell the drivers -how to identify them. This requires specifying the port address, the -protocol identification number and, for some devices, the drive's -chain ID. While your system is booting, a number of messages are -displayed on the console. Like all such messages, they can be -reviewed with the 'dmesg' command. Among those messages will be -some lines like:: - - paride: bpck registered as protocol 0 - paride: epat registered as protocol 1 - -The numbers will always be the same until you build a new kernel with -different protocol selections. You should note these numbers as you -will need them to identify the devices. + ================ ============ ======== + Manufacturer Model Protocol + ================ ============ ======== + MicroSolutions CD-ROM bpck + MicroSolutions PD drive bpck + MicroSolutions hard-drive bpck + MicroSolutions 8000t tape bpck + SyQuest EZ, SparQ epat + Imation Superdisk epat + Maxell Superdisk friq + Avatar Shark epat + FreeCom CD-ROM frpw + Hewlett-Packard 5GB Tape epat + Hewlett-Packard 7200e (CD) epat + Hewlett-Packard 7200e (CD-R) epat + ================ ============ ======== + +All parports and all protocol drivers are probed automatically unless probe=0 +parameter is used. So just "modprobe epat" is enough for a Imation SuperDisk +drive to work. + +Manual device creation:: + + # echo "port protocol mode unit delay" >/sys/bus/pata_parport/new_device + +where: + + ======== ================================================ + port parport name (or "auto" for all parports) + protocol protocol name (or "auto" for all protocols) + mode mode number (protocol-specific) or -1 for probe + unit unit number (for backpack only, see below) + delay I/O delay (see troubleshooting section below) + ======== ================================================ If you happen to be using a MicroSolutions backpack device, you will also need to know the unit ID number for each drive. This is usually the last two digits of the drive's serial number (but read MicroSolutions' documentation about this). -As an example, let's assume that you have a MicroSolutions PD/CD drive -with unit ID number 36 connected to the parallel port at 0x378, a SyQuest -EZ-135 connected to the chained port on the PD/CD drive and also an -Imation Superdisk connected to port 0x278. You could give the following -options on your boot command:: - - pd.drive0=0x378,1 pf.drive0=0x278,1 pf.drive1=0x378,0,36 - -In the last option, pf.drive1 configures device /dev/pf1, the 0x378 -is the parallel port base address, the 0 is the protocol registration -number and 36 is the chain ID. - -Please note: while PARIDE will work both with and without the -PARPORT parallel port sharing system that is included by the -"Parallel port support" option, PARPORT must be included and enabled -if you want to use chains of devices on the same parallel port. - -2.2 Loading and configuring PARIDE as modules ----------------------------------------------- - -It is much faster and simpler to get to understand the PARIDE drivers -if you use them as loadable kernel modules. - -Note 1: - using these drivers with the "kerneld" automatic module loading - system is not recommended for beginners, and is not documented here. - -Note 2: - if you build PARPORT support as a loadable module, PARIDE must - also be built as loadable modules, and PARPORT must be loaded before - the PARIDE modules. - -To use PARIDE, you must begin by:: - - insmod paride - -this loads a base module which provides a registry for the protocols, -among other tasks. - -Then, load as many of the protocol modules as you think you might need. -As you load each module, it will register the protocols that it supports, -and print a log message to your kernel log file and your console. For -example:: - - # insmod epat - paride: epat registered as protocol 0 - # insmod kbic - paride: k951 registered as protocol 1 - paride: k971 registered as protocol 2 - -Finally, you can load high-level drivers for each kind of device that -you have connected. By default, each driver will autoprobe for a single -device, but you can support up to four similar devices by giving their -individual co-ordinates when you load the driver. - -For example, if you had two no-name CD-ROM drives both using the -KingByte KBIC-951A adapter, one on port 0x378 and the other on 0x3bc -you could give the following command:: - - # insmod pcd drive0=0x378,1 drive1=0x3bc,1 - -For most adapters, giving a port address and protocol number is sufficient, -but check the source files in linux/drivers/block/paride for more -information. (Hopefully someone will write some man pages one day !). - -As another example, here's what happens when PARPORT is installed, and -a SyQuest EZ-135 is attached to port 0x378:: - - # insmod paride - paride: version 1.0 installed - # insmod epat - paride: epat registered as protocol 0 - # insmod pd - pd: pd version 1.0, major 45, cluster 64, nice 0 - pda: Sharing parport1 at 0x378 - pda: epat 1.0, Shuttle EPAT chip c3 at 0x378, mode 5 (EPP-32), delay 1 - pda: SyQuest EZ135A, 262144 blocks [128M], (512/16/32), removable media - pda: pda1 - -Note that the last line is the output from the generic partition table -scanner - in this case it reports that it has found a disk with one partition. - -2.3 Using a PARIDE device --------------------------- - -Once the drivers have been loaded, you can access PARIDE devices in the -same way as their traditional counterparts. You will probably need to -create the device "special files". Here is a simple script that you can -cut to a file and execute:: - - #!/bin/bash - # - # mkd -- a script to create the device special files for the PARIDE subsystem - # - function mkdev { - mknod $1 $2 $3 $4 ; chmod 0660 $1 ; chown root:disk $1 - } - # - function pd { - D=$( printf \\$( printf "x%03x" $[ $1 + 97 ] ) ) - mkdev pd$D b 45 $[ $1 * 16 ] - for P in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 - do mkdev pd$D$P b 45 $[ $1 * 16 + $P ] - done - } - # - cd /dev - # - for u in 0 1 2 3 ; do pd $u ; done - for u in 0 1 2 3 ; do mkdev pcd$u b 46 $u ; done - for u in 0 1 2 3 ; do mkdev pf$u b 47 $u ; done - for u in 0 1 2 3 ; do mkdev pt$u c 96 $u ; done - for u in 0 1 2 3 ; do mkdev npt$u c 96 $[ $u + 128 ] ; done - for u in 0 1 2 3 ; do mkdev pg$u c 97 $u ; done - # - # end of mkd - -With the device files and drivers in place, you can access PARIDE devices -like any other Linux device. For example, to mount a CD-ROM in pcd0, use:: - - mount /dev/pcd0 /cdrom - -If you have a fresh Avatar Shark cartridge, and the drive is pda, you -might do something like:: - - fdisk /dev/pda -- make a new partition table with - partition 1 of type 83 - - mke2fs /dev/pda1 -- to build the file system - - mkdir /shark -- make a place to mount the disk - - mount /dev/pda1 /shark - -Devices like the Imation superdisk work in the same way, except that -they do not have a partition table. For example to make a 120MB -floppy that you could share with a DOS system:: - - mkdosfs /dev/pf0 - mount /dev/pf0 /mnt - - -2.4 The pf driver ------------------- - -The pf driver is intended for use with parallel port ATAPI disk -devices. The most common devices in this category are PD drives -and LS-120 drives. Traditionally, media for these devices are not -partitioned. Consequently, the pf driver does not support partitioned -media. This may be changed in a future version of the driver. - -2.5 Using the pt driver ------------------------- - -The pt driver for parallel port ATAPI tape drives is a minimal driver. -It does not yet support many of the standard tape ioctl operations. -For best performance, a block size of 32KB should be used. You will -probably want to set the parallel port delay to 0, if you can. - -2.6 Using the pg driver ------------------------- - -The pg driver can be used in conjunction with the cdrecord program -to create CD-ROMs. Please get cdrecord version 1.6.1 or later -from ftp://ftp.fokus.gmd.de/pub/unix/cdrecord/ . To record CD-R media -your parallel port should ideally be set to EPP mode, and the "port delay" -should be set to 0. With those settings it is possible to record at 2x -speed without any buffer underruns. If you cannot get the driver to work -in EPP mode, try to use "bidirectional" or "PS/2" mode and 1x speeds only. +If you omit the parameters from the end, defaults will be used, e.g.: + +Probe all parports with all protocols:: + + # echo auto >/sys/bus/pata_parport/new_device + +Probe parport0 using protocol epat and mode 4 (EPP-16):: + + # echo "parport0 epat 4" >/sys/bus/pata_parport/new_device + +Probe parport0 using all protocols:: + + # echo "parport0 auto" >/sys/bus/pata_parport/new_device + +Probe all parports using protoocol epat:: + + # echo "auto epat" >/sys/bus/pata_parport/new_device + +Deleting devices:: + + # echo pata_parport.0 >/sys/bus/pata_parport/delete_device 3. Troubleshooting @@ -344,9 +169,9 @@ in EPP mode, try to use "bidirectional" or "PS/2" mode and 1x speeds only. 3.1 Use EPP mode if you can ---------------------------- -The most common problems that people report with the PARIDE drivers +The most common problems that people report with the pata_parport drivers concern the parallel port CMOS settings. At this time, none of the -PARIDE protocol modules support ECP mode, or any ECP combination modes. +protocol modules support ECP mode, or any ECP combination modes. If you are able to do so, please set your parallel port into EPP mode using your CMOS setup procedure. @@ -354,17 +179,14 @@ using your CMOS setup procedure. ------------------------- Some parallel ports cannot reliably transfer data at full speed. To -offset the errors, the PARIDE protocol modules introduce a "port +offset the errors, the protocol modules introduce a "port delay" between each access to the i/o ports. Each protocol sets a default value for this delay. In most cases, the user can override the default and set it to 0 - resulting in somewhat higher transfer rates. In some rare cases (especially with older 486 systems) the default delays are not long enough. if you experience corrupt data transfers, or unexpected failures, you may wish to increase the -port delay. The delay can be programmed using the "driveN" parameters -to each of the high-level drivers. Please see the notes above, or -read the comments at the beginning of the driver source files in -linux/drivers/block/paride. +port delay. 3.3 Some drives need a printer reset ------------------------------------- @@ -374,66 +196,12 @@ that do not always power up correctly. We have noticed this with some drives based on OnSpec and older Freecom adapters. In these rare cases, the adapter can often be reinitialised by issuing a "printer reset" on the parallel port. As the reset operation is potentially disruptive in -multiple device environments, the PARIDE drivers will not do it +multiple device environments, the pata_parport drivers will not do it automatically. You can however, force a printer reset by doing:: insmod lp reset=1 rmmod lp If you have one of these marginal cases, you should probably build -your paride drivers as modules, and arrange to do the printer reset -before loading the PARIDE drivers. - -3.4 Use the verbose option and dmesg if you need help ------------------------------------------------------- - -While a lot of testing has gone into these drivers to make them work -as smoothly as possible, problems will arise. If you do have problems, -please check all the obvious things first: does the drive work in -DOS with the manufacturer's drivers ? If that doesn't yield any useful -clues, then please make sure that only one drive is hooked to your system, -and that either (a) PARPORT is enabled or (b) no other device driver -is using your parallel port (check in /proc/ioports). Then, load the -appropriate drivers (you can load several protocol modules if you want) -as in:: - - # insmod paride - # insmod epat - # insmod bpck - # insmod kbic - ... - # insmod pd verbose=1 - -(using the correct driver for the type of device you have, of course). -The verbose=1 parameter will cause the drivers to log a trace of their -activity as they attempt to locate your drive. - -Use 'dmesg' to capture a log of all the PARIDE messages (any messages -beginning with paride:, a protocol module's name or a driver's name) and -include that with your bug report. You can submit a bug report in one -of two ways. Either send it directly to the author of the PARIDE suite, -by e-mail to grant@torque.net, or join the linux-parport mailing list -and post your report there. - -3.5 For more information or help ---------------------------------- - -You can join the linux-parport mailing list by sending a mail message -to: - - linux-parport-request@torque.net - -with the single word:: - - subscribe - -in the body of the mail message (not in the subject line). Please be -sure that your mail program is correctly set up when you do this, as -the list manager is a robot that will subscribe you using the reply -address in your mail headers. REMOVE any anti-spam gimmicks you may -have in your mail headers, when sending mail to the list server. - -You might also find some useful information on the linux-parport -web pages (although they are not always up to date) at - - http://web.archive.org/web/%2E/http://www.torque.net/parport/ +your pata_parport drivers as modules, and arrange to do the printer reset +before loading the pata_parport drivers. diff --git a/Documentation/admin-guide/blockdev/ramdisk.rst b/Documentation/admin-guide/blockdev/ramdisk.rst index b7c2268f8dec..9ce6101e8dd9 100644 --- a/Documentation/admin-guide/blockdev/ramdisk.rst +++ b/Documentation/admin-guide/blockdev/ramdisk.rst @@ -6,7 +6,7 @@ Using the RAM disk block device with Linux 1) Overview 2) Kernel Command Line Parameters - 3) Using "rdev -r" + 3) Using "rdev" 4) An Example of Creating a Compressed RAM Disk @@ -59,51 +59,27 @@ default is 4096 (4 MB). rd_size See ramdisk_size. -3) Using "rdev -r" ------------------- +3) Using "rdev" +--------------- -The usage of the word (two bytes) that "rdev -r" sets in the kernel image is -as follows. The low 11 bits (0 -> 10) specify an offset (in 1 k blocks) of up -to 2 MB (2^11) of where to find the RAM disk (this used to be the size). Bit -14 indicates that a RAM disk is to be loaded, and bit 15 indicates whether a -prompt/wait sequence is to be given before trying to read the RAM disk. Since -the RAM disk dynamically grows as data is being written into it, a size field -is not required. Bits 11 to 13 are not currently used and may as well be zero. -These numbers are no magical secrets, as seen below:: +"rdev" is an obsolete, deprecated, antiquated utility that could be used +to set the boot device in a Linux kernel image. - ./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF - ./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000 - ./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000 +Instead of using rdev, just place the boot device information on the +kernel command line and pass it to the kernel from the bootloader. -Consider a typical two floppy disk setup, where you will have the -kernel on disk one, and have already put a RAM disk image onto disk #2. +You can also pass arguments to the kernel by setting FDARGS in +arch/x86/boot/Makefile and specify in initrd image by setting FDINITRD in +arch/x86/boot/Makefile. -Hence you want to set bits 0 to 13 as 0, meaning that your RAM disk -starts at an offset of 0 kB from the beginning of the floppy. -The command line equivalent is: "ramdisk_start=0" +Some of the kernel command line boot options that may apply here are:: -You want bit 14 as one, indicating that a RAM disk is to be loaded. -The command line equivalent is: "load_ramdisk=1" - -You want bit 15 as one, indicating that you want a prompt/keypress -sequence so that you have a chance to switch floppy disks. -The command line equivalent is: "prompt_ramdisk=1" - -Putting that together gives 2^15 + 2^14 + 0 = 49152 for an rdev word. -So to create disk one of the set, you would do:: - - /usr/src/linux# cat arch/x86/boot/zImage > /dev/fd0 - /usr/src/linux# rdev /dev/fd0 /dev/fd0 - /usr/src/linux# rdev -r /dev/fd0 49152 + ramdisk_start=N + ramdisk_size=M If you make a boot disk that has LILO, then for the above, you would use:: - append = "ramdisk_start=0 load_ramdisk=1 prompt_ramdisk=1" - -Since the default start = 0 and the default prompt = 1, you could use:: - - append = "load_ramdisk=1" - + append = "ramdisk_start=N ramdisk_size=M" 4) An Example of Creating a Compressed RAM Disk ----------------------------------------------- @@ -151,12 +127,9 @@ f) Put the RAM disk image onto the floppy, after the kernel. Use an offset dd if=/tmp/ram_image.gz of=/dev/fd0 bs=1k seek=400 -g) Use "rdev" to set the boot device, RAM disk offset, prompt flag, etc. - For prompt_ramdisk=1, load_ramdisk=1, ramdisk_start=400, one would - have 2^15 + 2^14 + 400 = 49552:: - - rdev /dev/fd0 /dev/fd0 - rdev -r /dev/fd0 49552 +g) Make sure that you have already specified the boot information in + FDARGS and FDINITRD or that you use a bootloader to pass kernel + command line boot options to the kernel. That is it. You now have your boot/root compressed RAM disk floppy. Some users may wish to combine steps (d) and (f) by using a pipe. @@ -167,11 +140,14 @@ users may wish to combine steps (d) and (f) by using a pipe. Changelog: ---------- +SEPT-2020 : + + Removed usage of "rdev" + 10-22-04 : Updated to reflect changes in command line options, remove obsolete references, general cleanup. James Nelson (james4765@gmail.com) - 12-95 : Original Document diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst index 6eccf13219ff..ee2b0030d416 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -1,15 +1,15 @@ ======================================== -zram: Compressed RAM based block devices +zram: Compressed RAM-based block devices ======================================== Introduction ============ -The zram module creates RAM based block devices named /dev/zram<id> +The zram module creates RAM-based block devices named /dev/zram<id> (<id> = 0, 1, ...). Pages written to these disks are compressed and stored in memory itself. These disks allow very fast I/O and compression provides -good amounts of memory savings. Some of the usecases include /tmp storage, -use as swap disks, various caches under /var and maybe many more :) +good amounts of memory savings. Some of the use cases include /tmp storage, +use as swap disks, various caches under /var and maybe many more. :) Statistics for individual zram devices are exported through sysfs nodes at /sys/block/zram<id>/ @@ -43,17 +43,17 @@ The list of possible return codes: ======== ============================================================= -EBUSY an attempt to modify an attribute that cannot be changed once - the device has been initialised. Please reset device first; + the device has been initialised. Please reset device first. -ENOMEM zram was not able to allocate enough memory to fulfil your - needs; + needs. -EINVAL invalid input has been provided. ======== ============================================================= -If you use 'echo', the returned value that is changed by 'echo' utility, +If you use 'echo', the returned value is set by the 'echo' utility, and, in general case, something like:: echo 3 > /sys/block/zram0/max_comp_streams - if [ $? -ne 0 ]; + if [ $? -ne 0 ]; then handle_error fi @@ -65,7 +65,8 @@ should suffice. :: modprobe zram num_devices=4 - This creates 4 devices: /dev/zram{0,1,2,3} + +This creates 4 devices: /dev/zram{0,1,2,3} num_devices parameter is optional and tells zram how many devices should be pre-created. Default: 1. @@ -73,12 +74,12 @@ pre-created. Default: 1. 2) Set max number of compression streams ======================================== -Regardless the value passed to this attribute, ZRAM will always -allocate multiple compression streams - one per online CPUs - thus +Regardless of the value passed to this attribute, ZRAM will always +allocate multiple compression streams - one per online CPU - thus allowing several concurrent compression operations. The number of allocated compression streams goes down when some of the CPUs become offline. There is no single-compression-stream mode anymore, -unless you are running a UP system or has only 1 CPU online. +unless you are running a UP system or have only 1 CPU online. To find out how many streams are currently available:: @@ -89,7 +90,7 @@ To find out how many streams are currently available:: Using comp_algorithm device attribute one can see available and currently selected (shown in square brackets) compression algorithms, -change selected compression algorithm (once the device is initialised +or change the selected compression algorithm (once the device is initialised there is no way to change compression algorithm). Examples:: @@ -167,9 +168,9 @@ Examples:: zram provides a control interface, which enables dynamic (on-demand) device addition and removal. -In order to add a new /dev/zramX device, perform read operation on hot_add -attribute. This will return either new device's device id (meaning that you -can use /dev/zram<id>) or error code. +In order to add a new /dev/zramX device, perform a read operation on the hot_add +attribute. This will return either the new device's device id (meaning that you +can use /dev/zram<id>) or an error code. Example:: @@ -186,8 +187,8 @@ execute:: Per-device statistics are exported as various nodes under /sys/block/zram<id>/ -A brief description of exported device attributes. For more details please -read Documentation/ABI/testing/sysfs-block-zram. +A brief description of exported device attributes follows. For more details +please read Documentation/ABI/testing/sysfs-block-zram. ====================== ====== =============================================== Name access description @@ -245,13 +246,11 @@ whitespace: File /sys/block/zram<id>/mm_stat -The stat file represents device's mm statistics. It consists of a single +The mm_stat file represents the device's mm statistics. It consists of a single line of text and contains the following stats separated by whitespace: ================ ============================================================= orig_data_size uncompressed size of data stored in this disk. - This excludes same-element-filled pages (same_pages) since - no memory is allocated for them. Unit: bytes compr_data_size compressed size of data stored in this disk mem_used_total the amount of memory allocated for this disk. This @@ -261,17 +260,18 @@ line of text and contains the following stats separated by whitespace: Unit: bytes mem_limit the maximum amount of memory ZRAM can use to store the compressed data - mem_used_max the maximum amount of memory zram have consumed to + mem_used_max the maximum amount of memory zram has consumed to store the data same_pages the number of same element filled pages written to this disk. No memory is allocated for such pages. pages_compacted the number of pages freed during compaction huge_pages the number of incompressible pages + huge_pages_since the number of incompressible pages since zram set up ================ ============================================================= File /sys/block/zram<id>/bd_stat -The stat file represents device's backing device statistics. It consists of +The bd_stat file represents a device's backing device statistics. It consists of a single line of text and contains the following stats separated by whitespace: ============== ============================================================= @@ -315,10 +315,10 @@ To use the feature, admin should set up backing device via:: echo /dev/sda5 > /sys/block/zramX/backing_dev -before disksize setting. It supports only partition at this moment. -If admin want to use incompressible page writeback, they could do via:: +before disksize setting. It supports only partitions at this moment. +If admin wants to use incompressible page writeback, they could do it via:: - echo huge > /sys/block/zramX/write + echo huge > /sys/block/zramX/writeback To use idle page writeback, first, user need to declare zram pages as idle:: @@ -326,14 +326,37 @@ as idle:: echo all > /sys/block/zramX/idle From now on, any pages on zram are idle pages. The idle mark -will be removed until someone request access of the block. +will be removed until someone requests access of the block. IOW, unless there is access request, those pages are still idle pages. +Additionally, when CONFIG_ZRAM_TRACK_ENTRY_ACTIME is enabled pages can be +marked as idle based on how long (in seconds) it's been since they were +last accessed:: + + echo 86400 > /sys/block/zramX/idle + +In this example all pages which haven't been accessed in more than 86400 +seconds (one day) will be marked idle. Admin can request writeback of those idle pages at right timing via:: echo idle > /sys/block/zramX/writeback -With the command, zram writeback idle pages from memory to the storage. +With the command, zram will writeback idle pages from memory to the storage. + +Additionally, if a user choose to writeback only huge and idle pages +this can be accomplished with:: + + echo huge_idle > /sys/block/zramX/writeback + +If a user chooses to writeback only incompressible pages (pages that none of +algorithms can compress) this can be accomplished with:: + + echo incompressible > /sys/block/zramX/writeback + +If an admin wants to write a specific page in zram device to the backing device, +they could write a page index into the interface:: + + echo "page_index=1251" > /sys/block/zramX/writeback If there are lots of write IO with flash device, potentially, it has flash wearout problem so that admin needs to design write limitation @@ -341,18 +364,18 @@ to guarantee storage health for entire product life. To overcome the concern, zram supports "writeback_limit" feature. The "writeback_limit_enable"'s default value is 0 so that it doesn't limit -any writeback. IOW, if admin want to apply writeback budget, he should +any writeback. IOW, if admin wants to apply writeback budget, they should enable writeback_limit_enable via:: $ echo 1 > /sys/block/zramX/writeback_limit_enable Once writeback_limit_enable is set, zram doesn't allow any writeback -until admin set the budget via /sys/block/zramX/writeback_limit. +until admin sets the budget via /sys/block/zramX/writeback_limit. (If admin doesn't enable writeback_limit_enable, writeback_limit's value -assigned via /sys/block/zramX/writeback_limit is meaninless.) +assigned via /sys/block/zramX/writeback_limit is meaningless.) -If admin want to limit writeback as per-day 400M, he could do it +If admin wants to limit writeback as per-day 400M, they could do it like below:: $ MB_SHIFT=20 @@ -361,28 +384,109 @@ like below:: /sys/block/zram0/writeback_limit. $ echo 1 > /sys/block/zram0/writeback_limit_enable -If admin want to allow further write again once the bugdet is exausted, -he could do it like below:: +If admins want to allow further write again once the budget is exhausted, +they could do it like below:: $ echo $((400<<MB_SHIFT>>4K_SHIFT)) > \ /sys/block/zram0/writeback_limit -If admin want to see remaining writeback budget since he set:: +If an admin wants to see the remaining writeback budget since last set:: $ cat /sys/block/zramX/writeback_limit -If admin want to disable writeback limit, he could do:: +If an admin wants to disable writeback limit, they could do:: $ echo 0 > /sys/block/zramX/writeback_limit_enable -The writeback_limit count will reset whenever you reset zram(e.g., +The writeback_limit count will reset whenever you reset zram (e.g., system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of writeback happened until you reset the zram to allocate extra writeback budget in next setting is user's job. -If admin want to measure writeback count in a certain period, he could +If admin wants to measure writeback count in a certain period, they could know it via /sys/block/zram0/bd_stat's 3rd column. +recompression +------------- + +With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative +(secondary) compression algorithms. The basic idea is that alternative +compression algorithm can provide better compression ratio at a price of +(potentially) slower compression/decompression speeds. Alternative compression +algorithm can, for example, be more successful compressing huge pages (those +that default algorithm failed to compress). Another application is idle pages +recompression - pages that are cold and sit in the memory can be recompressed +using more effective algorithm and, hence, reduce zsmalloc memory usage. + +With CONFIG_ZRAM_MULTI_COMP, zram supports up to 4 compression algorithms: +one primary and up to 3 secondary ones. Primary zram compressor is explained +in "3) Select compression algorithm", secondary algorithms are configured +using recomp_algorithm device attribute. + +Example::: + + #show supported recompression algorithms + cat /sys/block/zramX/recomp_algorithm + #1: lzo lzo-rle lz4 lz4hc [zstd] + #2: lzo lzo-rle lz4 [lz4hc] zstd + +Alternative compression algorithms are sorted by priority. In the example +above, zstd is used as the first alternative algorithm, which has priority +of 1, while lz4hc is configured as a compression algorithm with priority 2. +Alternative compression algorithm's priority is provided during algorithms +configuration::: + + #select zstd recompression algorithm, priority 1 + echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm + + #select deflate recompression algorithm, priority 2 + echo "algo=deflate priority=2" > /sys/block/zramX/recomp_algorithm + +Another device attribute that CONFIG_ZRAM_MULTI_COMP enables is recompress, +which controls recompression. + +Examples::: + + #IDLE pages recompression is activated by `idle` mode + echo "type=idle" > /sys/block/zramX/recompress + + #HUGE pages recompression is activated by `huge` mode + echo "type=huge" > /sys/block/zram0/recompress + + #HUGE_IDLE pages recompression is activated by `huge_idle` mode + echo "type=huge_idle" > /sys/block/zramX/recompress + +The number of idle pages can be significant, so user-space can pass a size +threshold (in bytes) to the recompress knob: zram will recompress only pages +of equal or greater size::: + + #recompress all pages larger than 3000 bytes + echo "threshold=3000" > /sys/block/zramX/recompress + + #recompress idle pages larger than 2000 bytes + echo "type=idle threshold=2000" > /sys/block/zramX/recompress + +Recompression of idle pages requires memory tracking. + +During re-compression for every page, that matches re-compression criteria, +ZRAM iterates the list of registered alternative compression algorithms in +order of their priorities. ZRAM stops either when re-compression was +successful (re-compressed object is smaller in size than the original one) +and matches re-compression criteria (e.g. size threshold) or when there are +no secondary algorithms left to try. If none of the secondary algorithms can +successfully re-compressed the page such a page is marked as incompressible, +so ZRAM will not attempt to re-compress it in the future. + +This re-compression behaviour, when it iterates through the list of +registered compression algorithms, increases our chances of finding the +algorithm that successfully compresses a particular page. Sometimes, however, +it is convenient (and sometimes even necessary) to limit recompression to +only one particular algorithm so that it will not try any other algorithms. +This can be achieved by providing a algo=NAME parameter::: + + #use zstd algorithm only (if registered) + echo "type=huge algo=zstd" > /sys/block/zramX/recompress + memory tracking =============== @@ -393,9 +497,11 @@ pages of the process with*pagemap. If you enable the feature, you could see block state via /sys/kernel/debug/zram/zram0/block_state". The output is as follows:: - 300 75.033841 .wh. - 301 63.806904 s... - 302 63.806919 ..hi + 300 75.033841 .wh... + 301 63.806904 s..... + 302 63.806919 ..hi.. + 303 62.801919 ....r. + 304 146.781902 ..hi.n First column zram's block index. @@ -412,6 +518,10 @@ Third column huge page i: idle page + r: + recompressed page (secondary compression algorithm) + n: + none (including secondary) of algorithms could compress it First line of above example says 300th block is accessed at 75.033841sec and the block's state is huge so it is written back to the backing |