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commit f88c59f4657ac2e0bab8f51f60022ecbe7f12e2e
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Author: Wilco Dijkstra <wdijkstr@arm.com>
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Date: Fri May 17 18:16:20 2019 +0100
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Small tcache improvements
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Change the tcache->counts[] entries to uint16_t - this removes
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the limit set by char and allows a larger tcache. Remove a few
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redundant asserts.
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bench-malloc-thread with 4 threads is ~15% faster on Cortex-A72.
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Reviewed-by: DJ Delorie <dj@redhat.com>
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* malloc/malloc.c (MAX_TCACHE_COUNT): Increase to UINT16_MAX.
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(tcache_put): Remove redundant assert.
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(tcache_get): Remove redundant asserts.
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(__libc_malloc): Check tcache count is not zero.
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* manual/tunables.texi (glibc.malloc.tcache_count): Update maximum.
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(cherry picked from commit 1f50f2ad854c84ead522bfc7331b46dbe6057d53)
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diff --git a/malloc/malloc.c b/malloc/malloc.c
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index 998879aededf0d7c..e6a483d5cf7c4312 100644
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--- a/malloc/malloc.c
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+++ b/malloc/malloc.c
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@@ -321,6 +321,10 @@ __malloc_assert (const char *assertion, const char *file, unsigned int line,
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/* This is another arbitrary limit, which tunables can change. Each
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tcache bin will hold at most this number of chunks. */
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# define TCACHE_FILL_COUNT 7
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+
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+/* Maximum chunks in tcache bins for tunables. This value must fit the range
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+ of tcache->counts[] entries, else they may overflow. */
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+# define MAX_TCACHE_COUNT UINT16_MAX
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#endif
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@@ -2915,12 +2919,10 @@ typedef struct tcache_entry
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time), this is for performance reasons. */
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typedef struct tcache_perthread_struct
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{
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- char counts[TCACHE_MAX_BINS];
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+ uint16_t counts[TCACHE_MAX_BINS];
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tcache_entry *entries[TCACHE_MAX_BINS];
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} tcache_perthread_struct;
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-#define MAX_TCACHE_COUNT 127 /* Maximum value of counts[] entries. */
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-
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static __thread bool tcache_shutting_down = false;
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static __thread tcache_perthread_struct *tcache = NULL;
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@@ -2930,7 +2932,6 @@ static __always_inline void
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tcache_put (mchunkptr chunk, size_t tc_idx)
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{
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tcache_entry *e = (tcache_entry *) chunk2mem (chunk);
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- assert (tc_idx < TCACHE_MAX_BINS);
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/* Mark this chunk as "in the tcache" so the test in _int_free will
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detect a double free. */
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@@ -2947,8 +2948,6 @@ static __always_inline void *
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tcache_get (size_t tc_idx)
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{
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tcache_entry *e = tcache->entries[tc_idx];
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- assert (tc_idx < TCACHE_MAX_BINS);
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- assert (tcache->counts[tc_idx] > 0);
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tcache->entries[tc_idx] = e->next;
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--(tcache->counts[tc_idx]);
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e->key = NULL;
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@@ -3053,9 +3052,8 @@ __libc_malloc (size_t bytes)
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DIAG_PUSH_NEEDS_COMMENT;
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if (tc_idx < mp_.tcache_bins
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- /*&& tc_idx < TCACHE_MAX_BINS*/ /* to appease gcc */
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&& tcache
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- && tcache->entries[tc_idx] != NULL)
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+ && tcache->counts[tc_idx] > 0)
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{
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return tcache_get (tc_idx);
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}
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diff --git a/manual/tunables.texi b/manual/tunables.texi
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index 9dccf2ee7f8eec17..f6c49250e3889ddd 100644
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--- a/manual/tunables.texi
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+++ b/manual/tunables.texi
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@@ -188,7 +188,7 @@ per-thread cache. The default (and maximum) value is 1032 bytes on
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@deftp Tunable glibc.malloc.tcache_count
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The maximum number of chunks of each size to cache. The default is 7.
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-The upper limit is 127. If set to zero, the per-thread cache is effectively
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+The upper limit is 65535. If set to zero, the per-thread cache is effectively
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disabled.
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The approximate maximum overhead of the per-thread cache is thus equal
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