• Johannes Weiner's avatar
    zswap: memcg accounting · f4840ccf
    Johannes Weiner authored
    Applications can currently escape their cgroup memory containment when
    zswap is enabled.  This patch adds per-cgroup tracking and limiting of
    zswap backend memory to rectify this.
    
    The existing cgroup2 memory.stat file is extended to show zswap statistics
    analogous to what's in meminfo and vmstat.  Furthermore, two new control
    files, memory.zswap.current and memory.zswap.max, are added to allow
    tuning zswap usage on a per-workload basis.  This is important since not
    all workloads benefit from zswap equally; some even suffer compared to
    disk swap when memory contents don't compress well.  The optimal size of
    the zswap pool, and the threshold for writeback, also depends on the size
    of the workload's warm set.
    
    The implementation doesn't use a traditional page_counter transaction. 
    zswap is unconventional as a memory consumer in that we only know the
    amount of memory to charge once expensive compression has occurred.  If
    zwap is disabled or the limit is already exceeded we obviously don't want
    to compress page upon page only to reject them all.  Instead, the limit is
    checked against current usage, then we compress and charge.  This allows
    some limit overrun, but not enough to matter in practice.
    
    [hannes@cmpxchg.org: fix for CONFIG_SLOB builds]
      Link: https://lkml.kernel.org/r/YnwD14zxYjUJPc2w@cmpxchg.org
    [hannes@cmpxchg.org: opt out of cgroups v1]
      Link: https://lkml.kernel.org/r/Yn6it9mBYFA+/lTb@cmpxchg.org
    Link: https://lkml.kernel.org/r/20220510152847.230957-7-hannes@cmpxchg.orgSigned-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Roman Gushchin <guro@fb.com>
    Cc: Shakeel Butt <shakeelb@google.com>
    Cc: Seth Jennings <sjenning@redhat.com>
    Cc: Dan Streetman <ddstreet@ieee.org>
    Cc: Minchan Kim <minchan@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    f4840ccf
cgroup-v2.rst 106 KB