linux/fs/proc
Vladimir Davydov 33c3fc71c8 mm: introduce idle page tracking
Knowing the portion of memory that is not used by a certain application or
memory cgroup (idle memory) can be useful for partitioning the system
efficiently, e.g.  by setting memory cgroup limits appropriately.
Currently, the only means to estimate the amount of idle memory provided
by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the
access bit for all pages mapped to a particular process by writing 1 to
clear_refs, wait for some time, and then count smaps:Referenced.  However,
this method has two serious shortcomings:

 - it does not count unmapped file pages
 - it affects the reclaimer logic

To overcome these drawbacks, this patch introduces two new page flags,
Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap.
A page's Idle flag can only be set from userspace by setting bit in
/sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page,
and it is cleared whenever the page is accessed either through page tables
(it is cleared in page_referenced() in this case) or using the read(2)
system call (mark_page_accessed()). Thus by setting the Idle flag for
pages of a particular workload, which can be found e.g.  by reading
/proc/PID/pagemap, waiting for some time to let the workload access its
working set, and then reading the bitmap file, one can estimate the amount
of pages that are not used by the workload.

The Young page flag is used to avoid interference with the memory
reclaimer.  A page's Young flag is set whenever the Access bit of a page
table entry pointing to the page is cleared by writing to the bitmap file.
If page_referenced() is called on a Young page, it will add 1 to its
return value, therefore concealing the fact that the Access bit was
cleared.

Note, since there is no room for extra page flags on 32 bit, this feature
uses extended page flags when compiled on 32 bit.

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: kpageidle requires an MMU]
[akpm@linux-foundation.org: decouple from page-flags rework]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-10 13:29:01 -07:00
..
array.c capabilities: ambient capabilities 2015-09-04 16:54:41 -07:00
base.c /proc/$PID/cmdline: fixup empty ARGV case 2015-07-17 16:39:54 -07:00
cmdline.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
consoles.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
cpuinfo.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
devices.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
fd.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
fd.h proc: Move proc_fd() to fs/proc/fd.h 2013-05-01 17:29:39 -04:00
generic.c proc: Allow creating permanently empty directories that serve as mount points 2015-07-01 10:36:41 -05:00
inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2015-07-03 15:20:57 -07:00
internal.h proc: Allow creating permanently empty directories that serve as mount points 2015-07-01 10:36:41 -05:00
interrupts.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Kconfig fs, proc: add help for CONFIG_PROC_CHILDREN 2015-07-17 16:39:52 -07:00
kcore.c x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86 2015-07-18 03:42:51 +02:00
kmsg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
loadavg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Makefile proc: Implement /proc/thread-self to point at the directory of the current thread 2014-08-04 10:07:11 -07:00
meminfo.c fs/proc/meminfo.c: include cma info in proc/meminfo 2014-12-18 19:08:10 -08:00
namespaces.c don't pass nameidata to ->follow_link() 2015-05-10 22:20:15 -04:00
nommu.c vfs: add seq_file_path() helper 2015-06-23 18:01:07 -04:00
page.c mm: introduce idle page tracking 2015-09-10 13:29:01 -07:00
proc_net.c VFS: normal filesystems (and lustre): d_inode() annotations 2015-04-15 15:06:57 -04:00
proc_sysctl.c sysctl: Allow creating permanently empty directories that serve as mountpoints. 2015-07-01 10:36:39 -05:00
proc_tty.c proc: remove proc_tty_ldisc variable 2014-08-08 15:57:22 -07:00
root.c vfs: Commit to never having exectuables on proc and sysfs. 2015-07-10 10:39:25 -05:00
self.c don't pass nameidata to ->follow_link() 2015-05-10 22:20:15 -04:00
softirqs.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
stat.c genirq: Prevent proc race against freeing of irq descriptors 2014-12-13 13:33:07 +01:00
task_mmu.c mm: introduce idle page tracking 2015-09-10 13:29:01 -07:00
task_nommu.c vfs: add seq_file_path() helper 2015-06-23 18:01:07 -04:00
thread_self.c don't pass nameidata to ->follow_link() 2015-05-10 22:20:15 -04:00
uptime.c cputime: Default implementation of nsecs -> cputime conversion 2014-03-13 15:56:43 +01:00
version.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
vmcore.c vmcore: fix PT_NOTE n_namesz, n_descsz overflow issue 2015-02-17 14:34:52 -08:00