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authorWilco Dijkstra <wdijkstr@arm.com>2019-05-17 18:16:20 +0100
committerWilco Dijkstra <wdijkstr@arm.com>2019-05-17 18:16:20 +0100
commit1f50f2ad854c84ead522bfc7331b46dbe6057d53 (patch)
treea350b22461a9b819877711cf88a53f0191b388b5
parentfef7c63cd5a5a3150dc9465687359351afab5010 (diff)
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Small tcache improvements
Change the tcache->counts[] entries to uint16_t - this removes the limit set by char and allows a larger tcache. Remove a few redundant asserts. bench-malloc-thread with 4 threads is ~15% faster on Cortex-A72. Reviewed-by: DJ Delorie <dj@redhat.com> * malloc/malloc.c (MAX_TCACHE_COUNT): Increase to UINT16_MAX. (tcache_put): Remove redundant assert. (tcache_get): Remove redundant asserts. (__libc_malloc): Check tcache count is not zero. * manual/tunables.texi (glibc.malloc.tcache_count): Update maximum.
-rw-r--r--ChangeLog8
-rw-r--r--malloc/malloc.c14
-rw-r--r--manual/tunables.texi2
3 files changed, 15 insertions, 9 deletions
diff --git a/ChangeLog b/ChangeLog
index 1e445899181..da5cbd1dcce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-05-17 Wilco Dijkstra <wdijkstr@arm.com>
+
+ * malloc/malloc.c (MAX_TCACHE_COUNT): Increase to UINT16_MAX.
+ (tcache_put): Remove redundant assert.
+ (tcache_get): Remove redundant asserts.
+ (__libc_malloc): Check tcache count is not zero.
+ * manual/tunables.texi (glibc.malloc.tcache_count): Update maximum.
+
2019-05-17 Florian Weimer <fweimer@redhat.com>
* manual/llio.texi (Open-time Flags): Document O_DIRECTORY.
diff --git a/malloc/malloc.c b/malloc/malloc.c
index b8baaa2706d..00ce48cf587 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -321,6 +321,10 @@ __malloc_assert (const char *assertion, const char *file, unsigned int line,
/* This is another arbitrary limit, which tunables can change. Each
tcache bin will hold at most this number of chunks. */
# define TCACHE_FILL_COUNT 7
+
+/* Maximum chunks in tcache bins for tunables. This value must fit the range
+ of tcache->counts[] entries, else they may overflow. */
+# define MAX_TCACHE_COUNT UINT16_MAX
#endif
@@ -2901,12 +2905,10 @@ typedef struct tcache_entry
time), this is for performance reasons. */
typedef struct tcache_perthread_struct
{
- char counts[TCACHE_MAX_BINS];
+ uint16_t counts[TCACHE_MAX_BINS];
tcache_entry *entries[TCACHE_MAX_BINS];
} tcache_perthread_struct;
-#define MAX_TCACHE_COUNT 127 /* Maximum value of counts[] entries. */
-
static __thread bool tcache_shutting_down = false;
static __thread tcache_perthread_struct *tcache = NULL;
@@ -2916,7 +2918,6 @@ static __always_inline void
tcache_put (mchunkptr chunk, size_t tc_idx)
{
tcache_entry *e = (tcache_entry *) chunk2mem (chunk);
- assert (tc_idx < TCACHE_MAX_BINS);
/* Mark this chunk as "in the tcache" so the test in _int_free will
detect a double free. */
@@ -2933,8 +2934,6 @@ static __always_inline void *
tcache_get (size_t tc_idx)
{
tcache_entry *e = tcache->entries[tc_idx];
- assert (tc_idx < TCACHE_MAX_BINS);
- assert (tcache->counts[tc_idx] > 0);
tcache->entries[tc_idx] = e->next;
--(tcache->counts[tc_idx]);
e->key = NULL;
@@ -3046,9 +3045,8 @@ __libc_malloc (size_t bytes)
DIAG_PUSH_NEEDS_COMMENT;
if (tc_idx < mp_.tcache_bins
- /*&& tc_idx < TCACHE_MAX_BINS*/ /* to appease gcc */
&& tcache
- && tcache->entries[tc_idx] != NULL)
+ && tcache->counts[tc_idx] > 0)
{
return tcache_get (tc_idx);
}
diff --git a/manual/tunables.texi b/manual/tunables.texi
index ae638823a21..ee0fdf28d11 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -189,7 +189,7 @@ per-thread cache. The default (and maximum) value is 1032 bytes on
@deftp Tunable glibc.malloc.tcache_count
The maximum number of chunks of each size to cache. The default is 7.
-The upper limit is 127. If set to zero, the per-thread cache is effectively
+The upper limit is 65535. If set to zero, the per-thread cache is effectively
disabled.
The approximate maximum overhead of the per-thread cache is thus equal