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libio: Improve performance of IO locks 

Improve performance of recursive IO locks by adding a fast path for
the single-threaded case. To reduce the number of memory accesses for
locking/unlocking, only increment the recursion counter if the lock
is already taken.

On Neoverse V1, a microbenchmark with many small freads improved by
2.9x. Multithreaded performance improved by 2%.

Reviewed-by: Cristian Rodríguez  <crrodriguez@opensuse.org>
This commit is contained in:
Wilco Dijkstra 2022-08-11 16:47:45 +01:00
parent 11f09947f3
commit c51c483d2b
1 changed files with 19 additions and 9 deletions
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28
sysdeps/nptl/stdio-lock.h
View File

@ -37,12 +37,18 @@ typedef struct { int lock; int cnt; void *owner; } _IO_lock_t;
#define _IO_lock_lock(_name) \
do { \
void *__self = THREAD_SELF; \
if ((_name).owner != __self) \
if (SINGLE_THREAD_P && (_name).owner == NULL) \
{ \
(_name).lock = LLL_LOCK_INITIALIZER_LOCKED; \
(_name).owner = __self; \
} \
else if ((_name).owner != __self) \
{ \
lll_lock ((_name).lock, LLL_PRIVATE); \
(_name).owner = __self; \
(_name).owner = __self; \
} \
++(_name).cnt; \
else \
++(_name).cnt; \
} while (0)
#define _IO_lock_trylock(_name) \
@ -52,10 +58,7 @@ typedef struct { int lock; int cnt; void *owner; } _IO_lock_t;
if ((_name).owner != __self) \
{ \
if (lll_trylock ((_name).lock) == 0) \
{ \
(_name).owner = __self; \
(_name).cnt = 1; \
} \
(_name).owner = __self; \
else \
__result = EBUSY; \
} \
@ -66,11 +69,18 @@ typedef struct { int lock; int cnt; void *owner; } _IO_lock_t;
#define _IO_lock_unlock(_name) \
do { \
if (--(_name).cnt == 0) \
if (SINGLE_THREAD_P && (_name).cnt == 0) \
{ \
(_name).owner = NULL; \
(_name).owner = NULL; \
(_name).lock = 0; \
} \
else if ((_name).cnt == 0) \
{ \
(_name).owner = NULL; \
lll_unlock ((_name).lock, LLL_PRIVATE); \
} \
else \
--(_name).cnt; \
} while (0)