+ mm-memcg-do-not-set-reclaim_state-on-soft-limit-reclaim.patch added to -mm tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch titled
     Subject: mm, memcg: do not set reclaim_state on soft limit reclaim
has been added to the -mm tree.  Its filename is
     mm-memcg-do-not-set-reclaim_state-on-soft-limit-reclaim.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-do-not-set-reclaim_state-on-soft-limit-reclaim.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-do-not-set-reclaim_state-on-soft-limit-reclaim.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm, memcg: do not set reclaim_state on soft limit reclaim

Adric Blake has noticed[1] the following warning:
[38491.963105] WARNING: CPU: 7 PID: 175 at mm/vmscan.c:245 set_task_reclaim_state+0x1e/0x40
[...]
[38491.963239] Call Trace:
[38491.963246]  mem_cgroup_shrink_node+0x9b/0x1d0
[38491.963250]  mem_cgroup_soft_limit_reclaim+0x10c/0x3a0
[38491.963254]  balance_pgdat+0x276/0x540
[38491.963258]  kswapd+0x200/0x3f0
[38491.963261]  ? wait_woken+0x80/0x80
[38491.963265]  kthread+0xfd/0x130
[38491.963267]  ? balance_pgdat+0x540/0x540
[38491.963269]  ? kthread_park+0x80/0x80
[38491.963273]  ret_from_fork+0x35/0x40
[38491.963276] ---[ end trace 727343df67b2398a ]---

which tells us that soft limit reclaim is about to overwrite the
reclaim_state configured up in the call chain (kswapd in this case but the
direct reclaim is equally possible).  This means that reclaim stats would
get misleading once the soft reclaim returns and another reclaim is done.

Fix the warning by dropping set_task_reclaim_state from the soft reclaim
which is always called with reclaim_state set up.

[1] http://lkml.kernel.org/r/CAE1jjeePxYPvw1mw2B3v803xHVR_BNnz0hQUY_JDMN8ny29M6w@xxxxxxxxxxxxxx

Link: http://lkml.kernel.org/r/20190828071808.20410-1-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Adric Blake <promarbler14@xxxxxxxxx>
Acked-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Acked-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/vmscan.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/vmscan.c~mm-memcg-do-not-set-reclaim_state-on-soft-limit-reclaim
+++ a/mm/vmscan.c
@@ -3220,6 +3220,7 @@ unsigned long try_to_free_pages(struct z
 
 #ifdef CONFIG_MEMCG
 
+/* Only used by soft limit reclaim. Do not reuse for anything else. */
 unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
 						gfp_t gfp_mask, bool noswap,
 						pg_data_t *pgdat,
@@ -3235,7 +3236,8 @@ unsigned long mem_cgroup_shrink_node(str
 	};
 	unsigned long lru_pages;
 
-	set_task_reclaim_state(current, &sc.reclaim_state);
+	WARN_ON_ONCE(!current->reclaim_state);
+
 	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
 			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
 
@@ -3253,7 +3255,6 @@ unsigned long mem_cgroup_shrink_node(str
 
 	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
 
-	set_task_reclaim_state(current, NULL);
 	*nr_scanned = sc.nr_scanned;
 
 	return sc.nr_reclaimed;
_

Patches currently in -mm which might be from mhocko@xxxxxxxx are

mm-memcg-do-not-set-reclaim_state-on-soft-limit-reclaim.patch




[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux