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 3/3] readahead: trigger mmap sequential readahead on PG_readahead
Date: Sat, 30 Apr 2011 11:22:46 +0800 [thread overview]
Message-ID: <20110430033018.169293004@intel.com> (raw)
In-Reply-To: 20110430032243.355805181@intel.com
[-- Attachment #1: readahead-no-mmap-prev_pos.patch --]
[-- Type: text/plain, Size: 1884 bytes --]
Previously the mmap sequential readahead is triggered by updating
ra->prev_pos on each page fault and compare it with current page offset.
It costs dirtying the cache line on each _minor_ page fault. So remove
the ra->prev_pos recording, and instead tag PG_readahead to trigger the
possible sequential readahead. It's not only more simple, but also will
work more reliably and reduce cache line bouncing on concurrent page
faults on shared struct file.
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 | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- linux-next.orig/mm/filemap.c 2011-04-23 16:52:21.000000000 +0800
+++ linux-next/mm/filemap.c 2011-04-24 09:59:08.000000000 +0800
@@ -1531,8 +1531,7 @@ static void do_sync_mmap_readahead(struc
if (!ra->ra_pages)
return;
- if (VM_SequentialReadHint(vma) ||
- offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
+ if (VM_SequentialReadHint(vma)) {
page_cache_sync_readahead(mapping, ra, file, offset,
ra->ra_pages);
return;
@@ -1555,7 +1554,7 @@ static void do_sync_mmap_readahead(struc
ra_pages = max_sane_readahead(ra->ra_pages);
ra->start = max_t(long, 0, offset - ra_pages / 2);
ra->size = ra_pages;
- ra->async_size = 0;
+ ra->async_size = ra_pages / 4;
ra_submit(ra, mapping, file);
}
@@ -1661,7 +1660,6 @@ retry_find:
return VM_FAULT_SIGBUS;
}
- ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
vmf->page = page;
return ret | VM_FAULT_LOCKED;
--
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next prev parent reply other threads:[~2011-04-30 3:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
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
2011-04-30 3:22 ` [PATCH 2/3] readahead: reduce unnecessary mmap_miss increases Wu Fengguang
2011-04-30 3:22 ` Wu Fengguang
2011-04-30 3:22 ` Wu Fengguang [this message]
2011-04-30 3:22 ` [PATCH 3/3] readahead: trigger mmap sequential readahead on PG_readahead Wu Fengguang
-- strict thread matches above, loose matches on Subject: below --
2011-04-26 9:43 [PATCH 0/3] reduce readahead overheads on tmpfs mmap page faults Wu Fengguang
2011-04-26 9:43 ` [PATCH 3/3] readahead: trigger mmap sequential readahead on PG_readahead Wu Fengguang
2011-04-26 9:43 ` Wu Fengguang
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