vmscan: add shrink_slab tracepoints
It 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> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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@ -179,6 +179,83 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_memcg_softlimit_re
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TP_ARGS(nr_reclaimed)
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);
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TRACE_EVENT(mm_shrink_slab_start,
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TP_PROTO(struct shrinker *shr, struct shrink_control *sc,
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long nr_objects_to_shrink, unsigned long pgs_scanned,
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unsigned long lru_pgs, unsigned long cache_items,
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unsigned long long delta, unsigned long total_scan),
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TP_ARGS(shr, sc, nr_objects_to_shrink, pgs_scanned, lru_pgs,
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cache_items, delta, total_scan),
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TP_STRUCT__entry(
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__field(struct shrinker *, shr)
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__field(void *, shrink)
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__field(long, nr_objects_to_shrink)
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__field(gfp_t, gfp_flags)
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__field(unsigned long, pgs_scanned)
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__field(unsigned long, lru_pgs)
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__field(unsigned long, cache_items)
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__field(unsigned long long, delta)
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__field(unsigned long, total_scan)
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),
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TP_fast_assign(
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__entry->shr = shr;
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__entry->shrink = shr->shrink;
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__entry->nr_objects_to_shrink = nr_objects_to_shrink;
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__entry->gfp_flags = sc->gfp_mask;
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__entry->pgs_scanned = pgs_scanned;
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__entry->lru_pgs = lru_pgs;
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__entry->cache_items = cache_items;
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__entry->delta = delta;
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__entry->total_scan = total_scan;
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),
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TP_printk("%pF %p: objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
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__entry->shrink,
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__entry->shr,
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__entry->nr_objects_to_shrink,
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show_gfp_flags(__entry->gfp_flags),
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__entry->pgs_scanned,
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__entry->lru_pgs,
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__entry->cache_items,
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__entry->delta,
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__entry->total_scan)
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);
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TRACE_EVENT(mm_shrink_slab_end,
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TP_PROTO(struct shrinker *shr, int shrinker_retval,
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long unused_scan_cnt, long new_scan_cnt),
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TP_ARGS(shr, shrinker_retval, unused_scan_cnt, new_scan_cnt),
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TP_STRUCT__entry(
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__field(struct shrinker *, shr)
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__field(void *, shrink)
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__field(long, unused_scan)
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__field(long, new_scan)
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__field(int, retval)
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__field(long, total_scan)
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),
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TP_fast_assign(
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__entry->shr = shr;
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__entry->shrink = shr->shrink;
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__entry->unused_scan = unused_scan_cnt;
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__entry->new_scan = new_scan_cnt;
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__entry->retval = shrinker_retval;
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__entry->total_scan = new_scan_cnt - unused_scan_cnt;
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),
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TP_printk("%pF %p: unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
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__entry->shrink,
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__entry->shr,
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__entry->unused_scan,
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__entry->new_scan,
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__entry->total_scan,
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__entry->retval)
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);
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DECLARE_EVENT_CLASS(mm_vmscan_lru_isolate_template,
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@ -250,6 +250,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
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unsigned long long delta;
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unsigned long total_scan;
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unsigned long max_pass;
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int shrink_ret = 0;
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max_pass = do_shrinker_shrink(shrinker, shrink, 0);
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delta = (4 * nr_pages_scanned) / shrinker->seeks;
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@ -274,9 +275,12 @@ unsigned long shrink_slab(struct shrink_control *shrink,
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total_scan = shrinker->nr;
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shrinker->nr = 0;
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trace_mm_shrink_slab_start(shrinker, shrink, total_scan,
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nr_pages_scanned, lru_pages,
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max_pass, delta, total_scan);
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while (total_scan >= SHRINK_BATCH) {
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long this_scan = SHRINK_BATCH;
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int shrink_ret;
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int nr_before;
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nr_before = do_shrinker_shrink(shrinker, shrink, 0);
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@ -293,6 +297,8 @@ unsigned long shrink_slab(struct shrink_control *shrink,
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}
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shrinker->nr += total_scan;
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trace_mm_shrink_slab_end(shrinker, shrink_ret, total_scan,
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shrinker->nr);
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}
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up_read(&shrinker_rwsem);
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out:
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