diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/events.txt | 154 |
1 files changed, 148 insertions, 6 deletions
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt index db223e85bd2f..cc0216760b78 100644 --- a/Documentation/trace/events.txt +++ b/Documentation/trace/events.txt @@ -550,12 +550,14 @@ The following commands are supported: 'hist' triggers add a 'hist' file to each event's subdirectory. Reading the 'hist' file for the event will dump the hash table in - its entirety to stdout. Each printed hash table entry is a simple - list of the keys and values comprising the entry; keys are printed - first and are delineated by curly braces, and are followed by the - set of value fields for the entry. By default, numeric fields are - displayed as base-10 integers. This can be modified by appending - any of the following modifiers to the field name: + its entirety to stdout. If there are multiple hist triggers + attached to an event, there will be a table for each trigger in the + output. Each printed hash table entry is a simple list of the keys + and values comprising the entry; keys are printed first and are + delineated by curly braces, and are followed by the set of value + fields for the entry. By default, numeric fields are displayed as + base-10 integers. This can be modified by appending any of the + following modifiers to the field name: .hex display a number as a hex value .sym display an address as a symbol @@ -1667,3 +1669,143 @@ The following commands are supported: . . . + + The following example demonstrates how multiple hist triggers can be + attached to a given event. This capability can be useful for + creating a set of different summaries derived from the same set of + events, or for comparing the effects of different filters, among + other things. + + # echo 'hist:keys=skbaddr.hex:vals=len if len < 0' >> \ + /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger + # echo 'hist:keys=skbaddr.hex:vals=len if len > 4096' >> \ + /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger + # echo 'hist:keys=skbaddr.hex:vals=len if len == 256' >> \ + /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger + # echo 'hist:keys=skbaddr.hex:vals=len' >> \ + /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger + # echo 'hist:keys=len:vals=common_preempt_count' >> \ + /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger + + The above set of commands create four triggers differing only in + their filters, along with a completely different though fairly + nonsensical trigger. Note that in order to append multiple hist + triggers to the same file, you should use the '>>' operator to + append them ('>' will also add the new hist trigger, but will remove + any existing hist triggers beforehand). + + Displaying the contents of the 'hist' file for the event shows the + contents of all five histograms: + + # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist + + # event histogram + # + # trigger info: hist:keys=len:vals=hitcount,common_preempt_count:sort=hitcount:size=2048 [active] + # + + { len: 176 } hitcount: 1 common_preempt_count: 0 + { len: 223 } hitcount: 1 common_preempt_count: 0 + { len: 4854 } hitcount: 1 common_preempt_count: 0 + { len: 395 } hitcount: 1 common_preempt_count: 0 + { len: 177 } hitcount: 1 common_preempt_count: 0 + { len: 446 } hitcount: 1 common_preempt_count: 0 + { len: 1601 } hitcount: 1 common_preempt_count: 0 + . + . + . + { len: 1280 } hitcount: 66 common_preempt_count: 0 + { len: 116 } hitcount: 81 common_preempt_count: 40 + { len: 708 } hitcount: 112 common_preempt_count: 0 + { len: 46 } hitcount: 221 common_preempt_count: 0 + { len: 1264 } hitcount: 458 common_preempt_count: 0 + + Totals: + Hits: 1428 + Entries: 147 + Dropped: 0 + + + # event histogram + # + # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active] + # + + { skbaddr: ffff8800baee5e00 } hitcount: 1 len: 130 + { skbaddr: ffff88005f3d5600 } hitcount: 1 len: 1280 + { skbaddr: ffff88005f3d4900 } hitcount: 1 len: 1280 + { skbaddr: ffff88009fed6300 } hitcount: 1 len: 115 + { skbaddr: ffff88009fe0ad00 } hitcount: 1 len: 115 + { skbaddr: ffff88008cdb1900 } hitcount: 1 len: 46 + { skbaddr: ffff880064b5ef00 } hitcount: 1 len: 118 + { skbaddr: ffff880044e3c700 } hitcount: 1 len: 60 + { skbaddr: ffff880100065900 } hitcount: 1 len: 46 + { skbaddr: ffff8800d46bd500 } hitcount: 1 len: 116 + { skbaddr: ffff88005f3d5f00 } hitcount: 1 len: 1280 + { skbaddr: ffff880100064700 } hitcount: 1 len: 365 + { skbaddr: ffff8800badb6f00 } hitcount: 1 len: 60 + . + . + . + { skbaddr: ffff88009fe0be00 } hitcount: 27 len: 24677 + { skbaddr: ffff88009fe0a400 } hitcount: 27 len: 23052 + { skbaddr: ffff88009fe0b700 } hitcount: 31 len: 25589 + { skbaddr: ffff88009fe0b600 } hitcount: 32 len: 27326 + { skbaddr: ffff88006a462800 } hitcount: 68 len: 71678 + { skbaddr: ffff88006a463700 } hitcount: 70 len: 72678 + { skbaddr: ffff88006a462b00 } hitcount: 71 len: 77589 + { skbaddr: ffff88006a463600 } hitcount: 73 len: 71307 + { skbaddr: ffff88006a462200 } hitcount: 81 len: 81032 + + Totals: + Hits: 1451 + Entries: 318 + Dropped: 0 + + + # event histogram + # + # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len == 256 [active] + # + + + Totals: + Hits: 0 + Entries: 0 + Dropped: 0 + + + # event histogram + # + # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len > 4096 [active] + # + + { skbaddr: ffff88009fd2c300 } hitcount: 1 len: 7212 + { skbaddr: ffff8800d2bcce00 } hitcount: 1 len: 7212 + { skbaddr: ffff8800d2bcd700 } hitcount: 1 len: 7212 + { skbaddr: ffff8800d2bcda00 } hitcount: 1 len: 21492 + { skbaddr: ffff8800ae2e2d00 } hitcount: 1 len: 7212 + { skbaddr: ffff8800d2bcdb00 } hitcount: 1 len: 7212 + { skbaddr: ffff88006a4df500 } hitcount: 1 len: 4854 + { skbaddr: ffff88008ce47b00 } hitcount: 1 len: 18636 + { skbaddr: ffff8800ae2e2200 } hitcount: 1 len: 12924 + { skbaddr: ffff88005f3e1000 } hitcount: 1 len: 4356 + { skbaddr: ffff8800d2bcdc00 } hitcount: 2 len: 24420 + { skbaddr: ffff8800d2bcc200 } hitcount: 2 len: 12996 + + Totals: + Hits: 14 + Entries: 12 + Dropped: 0 + + + # event histogram + # + # trigger info: hist:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 if len < 0 [active] + # + + + Totals: + Hits: 0 + Entries: 0 + Dropped: 0 |