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    SubjectRe: [PATCH] mm/memcg: remove unneeded nr_scanned
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    On 2022/3/28 20:01, Michal Hocko wrote:
    > On Mon 28-03-22 19:41:44, Miaohe Lin wrote:
    >> The local variable nr_scanned is unneeded as mem_cgroup_soft_reclaim always
    >> does *total_scanned += nr_scanned. So we can pass total_scanned directly to
    >> the mem_cgroup_soft_reclaim to simplify the code and save some cpu cycles
    >> of adding nr_scanned to total_scanned.
    >
    > Maybe the compiler could be clever enough to generate a good code.
    > mem_cgroup_soft_reclaim doesn't have other caller so it could be
    > inlined. But I do agree that the change makes sense because it makes the
    > code more consistent as mem_cgroup_soft_limit_reclaim already uses
    > total_scanned this way.

    Many thanks for your comment and Acked-by tag. :)

    >
    >> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
    >
    > Acked-by: Michal Hocko <mhocko@suse.com>
    >
    > Thanks
    >
    >> ---
    >> mm/memcontrol.c | 5 +----
    >> 1 file changed, 1 insertion(+), 4 deletions(-)
    >>
    >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    >> index b686ec4f42c6..79341365ec90 100644
    >> --- a/mm/memcontrol.c
    >> +++ b/mm/memcontrol.c
    >> @@ -3384,7 +3384,6 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
    >> int loop = 0;
    >> struct mem_cgroup_tree_per_node *mctz;
    >> unsigned long excess;
    >> - unsigned long nr_scanned;
    >>
    >> if (order > 0)
    >> return 0;
    >> @@ -3412,11 +3411,9 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
    >> if (!mz)
    >> break;
    >>
    >> - nr_scanned = 0;
    >> reclaimed = mem_cgroup_soft_reclaim(mz->memcg, pgdat,
    >> - gfp_mask, &nr_scanned);
    >> + gfp_mask, total_scanned);
    >> nr_reclaimed += reclaimed;
    >> - *total_scanned += nr_scanned;
    >> spin_lock_irq(&mctz->lock);
    >> __mem_cgroup_remove_exceeded(mz, mctz);
    >>
    >> --
    >> 2.23.0
    >

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