[PATCH] aio: reorder kiocb structure elements to make sync iocb setup faster (59d9136b) · Commits · 戴 / test

Reorder members of the kiocb structure to make sync kiocb setup faster. By setting the elements sequentially, the write combining buffers on the CPU are able to combine the writes into a single burst, which results in fewer cache cycles being consumed, freeing them up for other code. This results in a 10-20KB/s[*] increase on the bw_unix part of LMbench on my test system. * The improvement varies based on what other patches are in the system, as there are a number of bottlenecks, so this number is not absolutely accurate. Signed-off-by:

Benjamin LaHaise <benjamin.c.lahaise@intel.com> Signed-off-by:

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

Linus Torvalds <torvalds@osdl.org>

include/linux/aio.h

+7 −5

Original line number	Diff line number	Diff line
		@@ -94,26 +94,27 @@ struct kiocb {
		ssize_t (ki_retry)(struct kiocb );
		void (ki_dtor)(struct kiocb );

		struct list_head ki_list; /* the aio core uses this
		* for cancellation */

		union {
		void __user *user;
		struct task_struct *tsk;
		} ki_obj;

		__u64 ki_user_data; /* user's data for completion */
		wait_queue_t ki_wait;
		loff_t ki_pos;

		void *private;
		/* State that we remember to be able to restart/retry */
		unsigned short ki_opcode;
		size_t ki_nbytes; /* copy of iocb->aio_nbytes */
		char __user ki_buf; / remaining iocb->aio_buf */
		size_t ki_left; /* remaining bytes */
		wait_queue_t ki_wait;
		long ki_retried; /* just for testing */
		long ki_kicked; /* just for testing */
		long ki_queued; /* just for testing */

		void *private;
		struct list_head ki_list; /* the aio core uses this
		* for cancellation */
		};

		#define is_sync_kiocb(iocb) ((iocb)->ki_key == KIOCB_SYNC_KEY)
		@@ -126,6 +127,7 @@ struct kiocb {
		(x)->ki_filp = (filp); \
		(x)->ki_ctx = NULL; \
		(x)->ki_cancel = NULL; \
		(x)->ki_retry = NULL; \
		(x)->ki_dtor = NULL; \
		(x)->ki_obj.tsk = tsk; \
		(x)->ki_user_data = 0; \

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