lkml.org 
[lkml]   [2020]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v2 2/3] mm/memcg: Simplify mem_cgroup_get_max()
    On Mon, Sep 14, 2020 at 05:29:06PM -0400, Johannes Weiner wrote:
    > On Mon, Sep 14, 2020 at 09:51:26AM -0400, Waiman Long wrote:
    > > On 9/14/20 7:48 AM, Michal Hocko wrote:
    > > > On Sun 13-09-20 22:44:51, Waiman Long wrote:
    > > > > The mem_cgroup_get_max() function used to get memory+swap max from
    > > > > both the v1 memsw and v2 memory+swap page counters & return the maximum
    > > > > of these 2 values. This is redundant and it is more efficient to just
    > > > > get either the v1 or the v2 values depending on which one is currently
    > > > > in use.
    > > > >
    > > > > Signed-off-by: Waiman Long <longman@redhat.com>
    > > > > ---
    > > > > mm/memcontrol.c | 20 +++++++++-----------
    > > > > 1 file changed, 9 insertions(+), 11 deletions(-)
    > > > >
    > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > > > > index 8c74f1200261..ca36bed588d1 100644
    > > > > --- a/mm/memcontrol.c
    > > > > +++ b/mm/memcontrol.c
    > > > > @@ -1633,17 +1633,15 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
    > > > > */
    > > > > unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)
    > > > > {
    > > > > - unsigned long max;
    > > > > -
    > > > > - max = READ_ONCE(memcg->memory.max);
    > > > > - if (mem_cgroup_swappiness(memcg)) {
    > > > > - unsigned long memsw_max;
    > > > > - unsigned long swap_max;
    > > > > -
    > > > > - memsw_max = memcg->memsw.max;
    > > > > - swap_max = READ_ONCE(memcg->swap.max);
    > > > > - swap_max = min(swap_max, (unsigned long)total_swap_pages);
    > > > > - max = min(max + swap_max, memsw_max);
    > > > > + unsigned long max = READ_ONCE(memcg->memory.max);
    > > > > +
    > > > > + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
    > > > > + if (mem_cgroup_swappiness(memcg))
    > > > > + max += min(READ_ONCE(memcg->swap.max),
    > > > > + (unsigned long)total_swap_pages);
    > > > > + } else { /* v1 */
    > > > > + if (mem_cgroup_swappiness(memcg))
    > > > > + max = memcg->memsw.max;
    > > > I agree that making v1 vs. v2 distinction here makes the code more
    > > > obvious. But I do not think your code is correct for v1. In a default
    > > > state it would lead to max = PAGE_COUNTER_MAX which is not something
    > > > we want, right?
    > > >
    > > > instead you want
    > > > max += min(READ_ONCE(memcg->memsw.max), total_swap_pages);
    > > >
    > > You are right, it is a bit tricky for v1.
    > >
    > > I will change it to
    > >
    > >     max += min(READ_ONCE(memcg->memsw.max) - max, total_swap_pages):
    >
    > memsw.max can be smaller than max.
    >
    > max = min3(max, READ_ONCE(memcg->memsw.max), total_swap_pages)?

    Nevermind, I saw the follow-up below, and it's indeed not allowed to
    configure it like that.

    \
     
     \ /
      Last update: 2020-09-14 23:33    [W:5.956 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site