[PATCH] aio: optimize io_submit_one()
This patch optimizes io_submit_one to call aio_run_iocb() directly if ctx->run_list is empty. When the list is empty, the operation of adding to the list, then call to __aio_run_iocbs() is unnecessary because these operations are done in one atomic step. ctx->run_list always has only one element in this case. This optimization speeds up industry standard db transaction processing benchmark by 0.2%. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Suparna Bhattacharya <suparna@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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fs/aio.c
12
fs/aio.c
@ -1514,10 +1514,14 @@ int fastcall io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
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goto out_put_req;
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spin_lock_irq(&ctx->ctx_lock);
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list_add_tail(&req->ki_run_list, &ctx->run_list);
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/* drain the run list */
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while (__aio_run_iocbs(ctx))
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;
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if (likely(list_empty(&ctx->run_list))) {
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aio_run_iocb(req);
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} else {
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list_add_tail(&req->ki_run_list, &ctx->run_list);
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/* drain the run list */
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while (__aio_run_iocbs(ctx))
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;
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}
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spin_unlock_irq(&ctx->ctx_lock);
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aio_put_req(req); /* drop extra ref to req */
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return 0;
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