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    Subject[PATCH 01/12] vmscan: add shrink_slab tracepoints
    Date
    From: Dave Chinner <dchinner@redhat.com>

    Іt is impossible to understand what the shrinkers are actually doing
    without instrumenting the code, so add a some tracepoints to allow
    insight to be gained.

    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    ---
    include/trace/events/vmscan.h | 67 +++++++++++++++++++++++++++++++++++++++++
    mm/vmscan.c | 6 +++-
    2 files changed, 72 insertions(+), 1 deletions(-)

    diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
    index ea422aa..c798cd7 100644
    --- a/include/trace/events/vmscan.h
    +++ b/include/trace/events/vmscan.h
    @@ -310,6 +310,73 @@ TRACE_EVENT(mm_vmscan_lru_shrink_inactive,
    show_reclaim_flags(__entry->reclaim_flags))
    );

    +TRACE_EVENT(mm_shrink_slab_start,
    + TP_PROTO(struct shrinker *shr, struct shrink_control *sc,
    + unsigned long pgs_scanned, unsigned long lru_pgs,
    + unsigned long cache_items, unsigned long long delta,
    + unsigned long total_scan),
    +
    + TP_ARGS(shr, sc, pgs_scanned, lru_pgs, cache_items, delta, total_scan),
    +
    + TP_STRUCT__entry(
    + __field(struct shrinker *, shr)
    + __field(long, shr_nr)
    + __field(gfp_t, gfp_flags)
    + __field(unsigned long, pgs_scanned)
    + __field(unsigned long, lru_pgs)
    + __field(unsigned long, cache_items)
    + __field(unsigned long long, delta)
    + __field(unsigned long, total_scan)
    + ),
    +
    + TP_fast_assign(
    + __entry->shr = shr;
    + __entry->shr_nr = shr->nr;
    + __entry->gfp_flags = sc->gfp_mask;
    + __entry->pgs_scanned = pgs_scanned;
    + __entry->lru_pgs = lru_pgs;
    + __entry->cache_items = cache_items;
    + __entry->delta = delta;
    + __entry->total_scan = total_scan;
    + ),
    +
    + TP_printk("shrinker %p: nr %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
    + __entry->shr,
    + __entry->shr_nr,
    + show_gfp_flags(__entry->gfp_flags),
    + __entry->pgs_scanned,
    + __entry->lru_pgs,
    + __entry->cache_items,
    + __entry->delta,
    + __entry->total_scan)
    +);
    +
    +TRACE_EVENT(mm_shrink_slab_end,
    + TP_PROTO(struct shrinker *shr, int shrinker_ret,
    + unsigned long total_scan),
    +
    + TP_ARGS(shr, shrinker_ret, total_scan),
    +
    + TP_STRUCT__entry(
    + __field(struct shrinker *, shr)
    + __field(long, shr_nr)
    + __field(int, shrinker_ret)
    + __field(unsigned long, total_scan)
    + ),
    +
    + TP_fast_assign(
    + __entry->shr = shr;
    + __entry->shr_nr = shr->nr;
    + __entry->shrinker_ret = shrinker_ret;
    + __entry->total_scan = total_scan;
    + ),
    +
    + TP_printk("shrinker %p: nr %ld total_scan %ld return val %d",
    + __entry->shr,
    + __entry->shr_nr,
    + __entry->total_scan,
    + __entry->shrinker_ret)
    +);

    #endif /* _TRACE_VMSCAN_H */

    diff --git a/mm/vmscan.c b/mm/vmscan.c
    index faa0a08..48e3fbd 100644
    --- a/mm/vmscan.c
    +++ b/mm/vmscan.c
    @@ -250,6 +250,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
    unsigned long long delta;
    unsigned long total_scan;
    unsigned long max_pass;
    + int shrink_ret = 0;

    max_pass = do_shrinker_shrink(shrinker, shrink, 0);
    delta = (4 * nr_pages_scanned) / shrinker->seeks;
    @@ -274,9 +275,11 @@ unsigned long shrink_slab(struct shrink_control *shrink,
    total_scan = shrinker->nr;
    shrinker->nr = 0;

    + trace_mm_shrink_slab_start(shrinker, shrink, nr_pages_scanned,
    + lru_pages, max_pass, delta, total_scan);
    +
    while (total_scan >= SHRINK_BATCH) {
    long this_scan = SHRINK_BATCH;
    - int shrink_ret;
    int nr_before;

    nr_before = do_shrinker_shrink(shrinker, shrink, 0);
    @@ -293,6 +296,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
    }

    shrinker->nr += total_scan;
    + trace_mm_shrink_slab_end(shrinker, shrink_ret, total_scan);
    }
    up_read(&shrinker_rwsem);
    out:
    --
    1.7.5.1
    --
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