ipc/sem.c: cacheline align the ipc spinlock for semaphores (31a7c474) · Commits · 戴 / test

Cacheline align the spinlock for sysv semaphores. Without the patch, the spinlock and sem_otime [written by every semop that modified the array] and sem_base [read in the hot path of try_atomic_semop()] can be in the same cacheline. Signed-off-by:

Manfred Spraul <manfred@colorfullife.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Zach Brown <zach.brown@oracle.com> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Nick Piggin <npiggin@suse.de> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sem.h

+3 −1

Original line number	Original line	Diff line number	Diff line
	@@ -79,6 +79,7 @@ struct seminfo {
	#ifdef __KERNEL__		#ifdef __KERNEL__
	#include <asm/atomic.h>		#include <asm/atomic.h>
	#include <linux/rcupdate.h>		#include <linux/rcupdate.h>
			#include <linux/cache.h>

	struct task_struct;		struct task_struct;

	@@ -91,7 +92,8 @@ struct sem {

	/* One sem_array data structure for each set of semaphores in the system. */		/* One sem_array data structure for each set of semaphores in the system. */
	struct sem_array {		struct sem_array {
	struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */		struct kern_ipc_perm ____cacheline_aligned_in_smp
			sem_perm; /* permissions .. see ipc.h */
	time_t sem_otime; /* last semop time */		time_t sem_otime; /* last semop time */
	time_t sem_ctime; /* last change time */		time_t sem_ctime; /* last change time */
	struct sem sem_base; / ptr to first semaphore in array */		struct sem sem_base; / ptr to first semaphore in array */

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