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    SubjectRe: [RFC PATCH] mm: memcontrol: don't account swap failures not due to cgroup limits
    On Thu, Feb 02, 2023 at 10:30:40AM -0800, Yosry Ahmed <yosryahmed@google.com> wrote:
    > > b) Only count cgroup swap events when they are actually due to a
    > > cgroup's own limit. Exclude failures that are due to physical swap
    > > shortage or other system-level conditions (like !THP_SWAP). Also
    > > count them at the level where the limit is configured, which may be
    > > above the local cgroup that holds the page-to-be-swapped.
    > >
    > > This is in line with how memory.swap.high, memory.high and
    > > memory.max events are counted.
    > >
    > > However, it's a change in documented behavior.
    >
    > This option makes sense to me, but I can't speak to the change of
    > documented behavior. However, looking at the code, it seems like if we do this
    > the "max" & "fail" counters become effectively the same. "fail" would
    > not provide much value then.
    >
    > I wonder if it makes sense to have both, and clarify that "fail" -
    > "max" would be non-limit based failures (e.g. ran out of swap space),
    > or would this cause confusion as to whether those non-limit failures
    > were transient (THP fallback) or eventual?

    I somewhat second this.

    Perhaps, could the patch (and arguments) be split in two:
    1) count .max events on respective limit's level (other limits consistency),
    2) redefine (remove?) memory.swap.fail events?

    Michal
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