From: Wu Fengguang <fengguang.wu@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Andi Kleen <andi@firstfloor.org>
Cc: Tim Chen <tim.c.chen@intel.com>,
Wu Fengguang <fengguang.wu@intel.com>,
Li Shaohua <shaohua.li@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: [PATCH 1/3] readahead: return early when readahead is disabled
Date: Tue, 26 Apr 2011 17:43:53 +0800 [thread overview]
Message-ID: <20110426094859.334469737@intel.com> (raw)
In-Reply-To: 20110426094352.030753173@intel.com
[-- Attachment #1: readahead-early-abort-mmap-around.patch --]
[-- Type: text/plain, Size: 1556 bytes --]
Reduce readahead overheads by returning early in
do_sync_mmap_readahead().
tmpfs has ra_pages=0 and it can page fault really fast
(not constraint by IO if not swapping).
Tested-by: Tim Chen <tim.c.chen@intel.com>
Reported-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/filemap.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- linux-next.orig/mm/filemap.c 2011-04-23 08:56:59.000000000 +0800
+++ linux-next/mm/filemap.c 2011-04-23 09:01:44.000000000 +0800
@@ -1528,6 +1528,8 @@ static void do_sync_mmap_readahead(struc
/* If we don't want any read-ahead, don't bother */
if (VM_RandomReadHint(vma))
return;
+ if (!ra->ra_pages)
+ return;
if (VM_SequentialReadHint(vma) ||
offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
@@ -1550,12 +1552,10 @@ static void do_sync_mmap_readahead(struc
* mmap read-around
*/
ra_pages = max_sane_readahead(ra->ra_pages);
- if (ra_pages) {
- ra->start = max_t(long, 0, offset - ra_pages/2);
- ra->size = ra_pages;
- ra->async_size = 0;
- ra_submit(ra, mapping, file);
- }
+ ra->start = max_t(long, 0, offset - ra_pages / 2);
+ ra->size = ra_pages;
+ ra->async_size = 0;
+ ra_submit(ra, mapping, file);
}
/*
--
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next prev parent reply other threads:[~2011-04-26 9:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-26 9:43 [PATCH 0/3] reduce readahead overheads on tmpfs mmap page faults Wu Fengguang
2011-04-26 9:43 ` [PATCH 1/3] readahead: return early when readahead is disabled Wu Fengguang
2011-04-26 9:43 ` Wu Fengguang [this message]
2011-04-26 9:43 ` [PATCH 2/3] readahead: reduce unnecessary mmap_miss increases Wu Fengguang
2011-04-26 9:43 ` Wu Fengguang
2011-04-26 9:43 ` [PATCH 3/3] readahead: trigger mmap sequential readahead on PG_readahead Wu Fengguang
2011-04-26 14:36 ` [PATCH 3/3 with new changelog] " Wu Fengguang
2011-04-26 9:43 ` [PATCH 3/3] " Wu Fengguang
-- strict thread matches above, loose matches on Subject: below --
2011-04-30 3:22 [PATCH 0/3] reduce readahead overheads on tmpfs mmap page faults v2 Wu Fengguang
2011-04-30 3:22 ` [PATCH 1/3] readahead: return early when readahead is disabled Wu Fengguang
2011-04-30 3:22 ` Wu Fengguang
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