From 5a6e75f8110c97e2a5488894d4e922187e6cb343 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Tue, 26 Jul 2016 15:26:13 -0700 Subject: shmem: prepare huge= mount option and sysfs knob This patch adds new mount option "huge=". It can have following values: - "always": Attempt to allocate huge pages every time we need a new page; - "never": Do not allocate huge pages; - "within_size": Only allocate huge page if it will be fully within i_size. Also respect fadvise()/madvise() hints; - "advise: Only allocate huge pages if requested with fadvise()/madvise(); Default is "never" for now. "mount -o remount,huge= /mountpoint" works fine after mount: remounting huge=never will not attempt to break up huge pages at all, just stop more from being allocated. No new config option: put this under CONFIG_TRANSPARENT_HUGEPAGE, which is the appropriate option to protect those who don't want the new bloat, and with which we shall share some pmd code. Prohibit the option when !CONFIG_TRANSPARENT_HUGEPAGE, just as mpol is invalid without CONFIG_NUMA (was hidden in mpol_parse_str(): make it explicit). Allow enabling THP only if the machine has_transparent_hugepage(). But what about Shmem with no user-visible mount? SysV SHM, memfds, shared anonymous mmaps (of /dev/zero or MAP_ANONYMOUS), GPU drivers' DRM objects, Ashmem. Though unlikely to suit all usages, provide sysfs knob /sys/kernel/mm/transparent_hugepage/shmem_enabled to experiment with huge on those. And allow shmem_enabled two further values: - "deny": For use in emergencies, to force the huge option off from all mounts; - "force": Force the huge option on for all - very useful for testing; Based on patch by Hugh Dickins. Link: http://lkml.kernel.org/r/1466021202-61880-28-git-send-email-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/huge_mm.h | 2 ++ include/linux/shmem_fs.h | 3 ++- 2 files changed, 4 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 254aac4c3963..2f757132662a 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -41,6 +41,8 @@ enum transparent_hugepage_flag { #endif }; +extern struct kobj_attribute shmem_enabled_attr; + #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT) #define HPAGE_PMD_NR (1<