From: Dave Kleikamp <dave.kleikamp@oracle.com>
Date: Tue, 13 Dec 2011 19:49:16 +0000 (-0600)
Subject: AIO: Don't plug the I/O queue in do_io_submit()
X-Git-Tag: v2.6.39-400.9.0~827^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3b87cb2d466dddfe3eba2d8f91214e86120616c9;p=users%2Fjedix%2Flinux-maple.git

AIO: Don't plug the I/O queue in do_io_submit()

Asynchronous I/O latency to a solid-state disk greatly increased
between the 2.6.32 and 3.0 kernels. By removing the plug from
do_io_submit(), we observed a 34% improvement in the I/O latency.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
---

diff --git a/fs/aio.c b/fs/aio.c
index e29ec485af25..75e05c91605d 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1622,7 +1622,6 @@ long do_io_submit(aio_context_t ctx_id, long nr,
 	struct kioctx *ctx;
 	long ret = 0;
 	int i;
-	struct blk_plug plug;
 
 	if (unlikely(nr < 0))
 		return -EINVAL;
@@ -1639,8 +1638,6 @@ long do_io_submit(aio_context_t ctx_id, long nr,
 		return -EINVAL;
 	}
 
-	blk_start_plug(&plug);
-
 	/*
 	 * AKPM: should this return a partial result if some of the IOs were
 	 * successfully submitted?
@@ -1663,7 +1660,6 @@ long do_io_submit(aio_context_t ctx_id, long nr,
 		if (ret)
 			break;
 	}
-	blk_finish_plug(&plug);
 
 	put_ioctx(ctx);
 	return i ? i : ret;