linux.git/mm/thrash.c, branch master

mm: remove swap token code

2012-05-29T23:22:19+00:00

The swap token code no longer fits in with the current VM model.  It
does not play well with cgroups or the better NUMA placement code in
development, since we have only one swap token globally.

It also has the potential to mess with scalability of the system, by
increasing the number of non-reclaimable pages on the active and
inactive anon LRU lists.

Last but not least, the swap token code has been broken for a year
without complaints, as reported by Konstantin Khlebnikov.  This suggests
we no longer have much use for it.

The days of sub-1G memory systems with heavy use of swap are over.  If
we ever need thrashing reducing code in the future, we will have to
implement something that does scale.

Signed-off-by: Rik van Riel 
Cc: Konstantin Khlebnikov 
Acked-by: Johannes Weiner 
Cc: Mel Gorman 
Cc: Hugh Dickins 
Acked-by: Bob Picco 
Acked-by: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/thrash.c: quiet sparse noise

2011-11-01T00:30:50+00:00

Quiet the following sparse noise:

warning: symbol 'swap_token_memcg' was not declared. Should it be static?

Signed-off-by: H Hartley Sweeten 
Cc: Rik van Riel 
Cc: KOSAKI Motohiro 
Cc: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: swap-token: add a comment for priority aging

2011-07-26T03:57:08+00:00

Document some swap token aging design decisions.

Signed-off-by: KOSAKI Motohiro 
Acked-by: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: swap-token: makes global variables to function local

2011-07-26T03:57:08+00:00

global_faults and last_aging are only used in grab_swap_token().  Move
them into grab_swap_token().

Signed-off-by: KOSAKI Motohiro 
Acked-by: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: swap-token: fix dead link

2011-07-26T03:57:08+00:00

http://www.cs.wm.edu/~sjiang/token.pdf is now dead.  Replace it with an
alive alternative.

Signed-off-by: KOSAKI Motohiro 
Acked-by: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vmscan: implement swap token priority aging

2011-06-16T03:03:59+00:00

While testing for memcg aware swap token, I observed a swap token was
often grabbed an intermittent running process (eg init, auditd) and they
never release a token.

Why?

Some processes (eg init, auditd, audispd) wake up when a process exiting.
And swap token can be get first page-in process when a process exiting
makes no swap token owner.  Thus such above intermittent running process
often get a token.

And currently, swap token priority is only decreased at page fault path.
Then, if the process sleep immediately after to grab swap token, the swap
token priority never be decreased.  That's obviously undesirable.

This patch implement very poor (and lightweight) priority aging.  It only
be affect to the above corner case and doesn't change swap tendency
workload performance (eg multi process qsbench load)

Signed-off-by: KOSAKI Motohiro 
Reviewed-by: Rik van Riel 
Reviewed-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vmscan: implement swap token trace

2011-06-16T03:03:59+00:00

This is useful for observing swap token activity.

example output:

             zsh-1845  [000]   598.962716: update_swap_token_priority:
mm=ffff88015eaf7700 old_prio=1 new_prio=0
          memtoy-1830  [001]   602.033900: update_swap_token_priority:
mm=ffff880037a45880 old_prio=947 new_prio=949
          memtoy-1830  [000]   602.041509: update_swap_token_priority:
mm=ffff880037a45880 old_prio=949 new_prio=951
          memtoy-1830  [000]   602.051959: update_swap_token_priority:
mm=ffff880037a45880 old_prio=951 new_prio=953
          memtoy-1830  [000]   602.052188: update_swap_token_priority:
mm=ffff880037a45880 old_prio=953 new_prio=955
          memtoy-1830  [001]   602.427184: put_swap_token:
token_mm=ffff880037a45880
             zsh-1789  [000]   602.427281: replace_swap_token:
old_token_mm=          (null) old_prio=0 new_token_mm=ffff88015eaf7018
new_prio=2
             zsh-1789  [001]   602.433456: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=2 new_prio=4
             zsh-1789  [000]   602.437613: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=4 new_prio=6
             zsh-1789  [000]   602.443924: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=6 new_prio=8
             zsh-1789  [000]   602.451873: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=8 new_prio=10
             zsh-1789  [001]   602.462639: update_swap_token_priority:
mm=ffff88015eaf7018 old_prio=10 new_prio=12

Signed-off-by: KOSAKI Motohiro 
Acked-by: Rik van Riel
Reviewed-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vmscan,memcg: memcg aware swap token

2011-06-16T03:03:59+00:00

Currently, memcg reclaim can disable swap token even if the swap token mm
doesn't belong in its memory cgroup.  It's slightly risky.  If an admin
creates very small mem-cgroup and silly guy runs contentious heavy memory
pressure workload, every tasks are going to lose swap token and then
system may become unresponsive.  That's bad.

This patch adds 'memcg' parameter into disable_swap_token().  and if the
parameter doesn't match swap token, VM doesn't disable it.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KOSAKI Motohiro 
Reviewed-by: KAMEZAWA Hiroyuki 
Reviewed-by: Rik van Riel
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: pass mm to grab_swap_token

2009-06-23T19:50:05+00:00

If a kthread happens to use get_user_pages() on an mm (as KSM does),
there's a chance that it will end up trying to read in a swap page, then
oops in grab_swap_token() because the kthread has no mm: GUP passes down
the right mm, so grab_swap_token() ought to be using it.

We have not identified a stronger case than KSM's daemon (not yet in
mainline), but the issue must have come up before, since RHEL has included
a fix for this for years (though a different fix, they just back out of
grab_swap_token if current->mm is unset: which is what we first proposed,
but using the right mm here seems more correct).

Reported-by: Izik Eidus 
Signed-off-by: Johannes Weiner 
Signed-off-by: Hugh Dickins 
Acked-by: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Bug in mm/thrash.c function grab_swap_token()

2007-05-11T15:29:32+00:00

Following bug was uncovered by compiling with '-W' flag:

  CC      mm/thrash.o
mm/thrash.c: In function âgrab_swap_tokenâ:
mm/thrash.c:52: warning: comparison of unsigned expression < 0 is always false

Variable token_priority is unsigned, so decrementing first and then
checking the result does not work; fixed by reversing the test, patch
attached (compile tested only).

I am not sure if likely() makes much sense in this new situation, but
I'll let somebody else to make a decision on that.

Signed-off-by: Mika Kukkonen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds