Tweak chunk purge order according to fragmentation.
Tweak chunk purge order to purge unfragmented chunks from high to low memory. This facilitates dirty run reuse.
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ed90c97332
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abf6739317
37
src/arena.c
37
src/arena.c
@ -138,14 +138,22 @@ rb_gen(static UNUSED, arena_avail_tree_, arena_avail_tree_t, arena_chunk_map_t,
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static inline int
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arena_chunk_dirty_comp(arena_chunk_t *a, arena_chunk_t *b)
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{
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size_t a_val, b_val;
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assert(a != NULL);
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assert(b != NULL);
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/*
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* Short-circuit for self comparison. The following comparison code
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* would come to the same result, but at the cost of executing the slow
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* path.
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*/
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if (a == b)
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return (0);
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/*
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* Order such that chunks with higher fragmentation are "less than"
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* those with lower fragmentation. Fragmentation is measured as:
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* those with lower fragmentation -- purging order is from "least" to
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* "greatest". Fragmentation is measured as:
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*
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* mean current avail run size
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* --------------------------------
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@ -163,18 +171,33 @@ arena_chunk_dirty_comp(arena_chunk_t *a, arena_chunk_t *b)
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* comparison, in order to avoid division.
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*
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*/
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a_val = (a->nruns_avail - a->nruns_adjac) * b->nruns_avail;
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b_val = (b->nruns_avail - b->nruns_adjac) * a->nruns_avail;
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{
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size_t a_val = (a->nruns_avail - a->nruns_adjac) *
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b->nruns_avail;
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size_t b_val = (b->nruns_avail - b->nruns_adjac) *
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a->nruns_avail;
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if (a_val < b_val)
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return (1);
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if (a_val > b_val)
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return (-1);
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/* Break ties by chunk address. */
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}
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/*
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* Break ties by chunk address. For fragmented chunks, report lower
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* addresses as "lower", so that fragmentation reduction happens first
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* at lower addresses. However, use the opposite ordering for
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* unfragmented chunks, in order to increase the chances of
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* re-allocating dirty runs.
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*/
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{
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uintptr_t a_chunk = (uintptr_t)a;
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uintptr_t b_chunk = (uintptr_t)b;
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return ((a_chunk > b_chunk) - (a_chunk < b_chunk));
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int ret = ((a_chunk > b_chunk) - (a_chunk < b_chunk));
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if (a->nruns_adjac == 0) {
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assert(b->nruns_adjac == 0);
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ret = -ret;
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}
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return (ret);
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}
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}
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