lkml.org 
[lkml]   [2019]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] Partially revert "mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones"
    On Fri, Aug 16, 2019 at 05:47:26PM -0700, Roman Gushchin wrote:
    > Commit 766a4c19d880 ("mm/memcontrol.c: keep local VM counters in sync
    > with the hierarchical ones") effectively decreased the precision of
    > per-memcg vmstats_local and per-memcg-per-node lruvec percpu counters.
    >
    > That's good for displaying in memory.stat, but brings a serious regression
    > into the reclaim process.
    >
    > One issue I've discovered and debugged is the following:
    > lruvec_lru_size() can return 0 instead of the actual number of pages
    > in the lru list, preventing the kernel to reclaim last remaining
    > pages. Result is yet another dying memory cgroups flooding.
    > The opposite is also happening: scanning an empty lru list
    > is the waste of cpu time.
    >
    > Also, inactive_list_is_low() can return incorrect values, preventing
    > the active lru from being scanned and freed. It can fail both because
    > the size of active and inactive lists are inaccurate, and because
    > the number of workingset refaults isn't precise. In other words,
    > the result is pretty random.
    >
    > I'm not sure, if using the approximate number of slab pages in
    > count_shadow_number() is acceptable, but issues described above
    > are enough to partially revert the patch.
    >
    > Let's keep per-memcg vmstat_local batched (they are only used for
    > displaying stats to the userspace), but keep lruvec stats precise.
    > This change fixes the dead memcg flooding on my setup.
    >
    > Fixes: 766a4c19d880 ("mm/memcontrol.c: keep local VM counters in sync with the hierarchical ones")
    > Signed-off-by: Roman Gushchin <guro@fb.com>
    > Cc: Yafang Shao <laoar.shao@gmail.com>
    > Cc: Johannes Weiner <hannes@cmpxchg.org>
    > ---
    > mm/memcontrol.c | 8 +++-----
    > 1 file changed, 3 insertions(+), 5 deletions(-)

    <formletter>

    This is not the correct way to submit patches for inclusion in the
    stable kernel tree. Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
    for how to do this properly.

    </formletter>

    \
     
     \ /
      Last update: 2019-08-17 08:40    [W:4.192 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site