From: Wu Fengguang <fengguang.wu@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jens.axboe@oracle.com>, Nick Piggin <npiggin@suse.de>,
Wu Fengguang <fengguang.wu@intel.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: Olivier Galibert <galibert@pobox.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 15/15] readahead: pagecache context based mmap read-around
Date: Wed, 24 Feb 2010 11:10:16 +0800 [thread overview]
Message-ID: <20100224031055.738182009@intel.com> (raw)
In-Reply-To: 20100224031001.026464755@intel.com
[-- Attachment #1: readahead-mmap-around-context.patch --]
[-- Type: text/plain, Size: 1540 bytes --]
Do mmap read-around when there are cached pages in the nearby 256KB
(covered by one radix tree node).
There is a failure case though: for a sequence of page faults at page
index 64*i+1, i=1,2,3,..., this heuristic will keep doing pointless
read-arounds. Hopefully the pattern won't appear in real workloads.
Note that the readahead heuristic has similiar failure case.
CC: Nick Piggin <npiggin@suse.de>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/filemap.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- linux.orig/mm/filemap.c 2010-02-23 13:20:39.000000000 +0800
+++ linux/mm/filemap.c 2010-02-23 13:22:36.000000000 +0800
@@ -1421,11 +1421,17 @@ static void do_sync_mmap_readahead(struc
/*
- * Do we miss much more than hit in this file? If so,
- * stop bothering with read-ahead. It will only hurt.
+ * Do we miss much more than hit in this file? If so, stop bothering
+ * with read-around, unless some nearby pages were accessed recently.
*/
- if (ra_mmap_miss_inc(ra) > MMAP_LOTSAMISS)
- return;
+ if (ra_mmap_miss_inc(ra) > MMAP_LOTSAMISS) {
+ struct radix_tree_node *node;
+ rcu_read_lock();
+ node = radix_tree_lookup_leaf_node(&mapping->page_tree, offset);
+ rcu_read_unlock();
+ if (!node)
+ return;
+ }
/*
* mmap read-around
--
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next prev parent reply other threads:[~2010-02-24 3:10 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-24 3:10 [PATCH 00/15] 512K readahead size with thrashing safe readahead v2 Wu Fengguang
2010-02-24 3:10 ` [PATCH 01/15] readahead: limit readahead size for small devices Wu Fengguang
2010-02-25 3:11 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 02/15] readahead: retain inactive lru pages to be accessed soon Wu Fengguang
2010-02-25 3:17 ` Rik van Riel
2010-02-25 12:27 ` Wu Fengguang
2010-02-24 3:10 ` [PATCH 03/15] readahead: bump up the default readahead size Wu Fengguang
2010-02-25 4:02 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 04/15] readahead: make default readahead size a kernel parameter Wu Fengguang
2010-02-25 14:59 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 05/15] readahead: limit readahead size for small memory systems Wu Fengguang
2010-02-25 15:00 ` Rik van Riel
2010-02-25 15:25 ` Christian Ehrhardt
2010-02-26 2:29 ` Wu Fengguang
2010-02-26 2:48 ` [PATCH] readahead: add notes on readahead size Wu Fengguang
2010-02-26 14:17 ` Vivek Goyal
2010-02-26 7:23 ` [PATCH 05/15] readahead: limit readahead size for small memory systems Christian Ehrhardt
2010-02-26 7:38 ` Wu Fengguang
2010-02-24 3:10 ` [PATCH 06/15] readahead: replace ra->mmap_miss with ra->ra_flags Wu Fengguang
2010-02-25 15:52 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 07/15] readahead: thrashing safe context readahead Wu Fengguang
2010-02-25 16:24 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 08/15] readahead: record readahead patterns Wu Fengguang
2010-02-25 22:37 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 09/15] readahead: add tracing event Wu Fengguang
2010-02-25 22:38 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 10/15] readahead: add /debug/readahead/stats Wu Fengguang
2010-02-25 22:40 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 11/15] readahead: dont do start-of-file readahead after lseek() Wu Fengguang
2010-02-25 22:42 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 12/15] radixtree: introduce radix_tree_lookup_leaf_node() Wu Fengguang
2010-02-25 23:13 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 13/15] radixtree: speed up the search for hole Wu Fengguang
2010-02-25 23:37 ` Rik van Riel
2010-02-24 3:10 ` [PATCH 14/15] readahead: reduce MMAP_LOTSAMISS for mmap read-around Wu Fengguang
2010-02-25 23:42 ` Rik van Riel
2010-02-24 3:10 ` Wu Fengguang [this message]
2010-02-26 1:33 ` [PATCH 15/15] readahead: pagecache context based " Rik van Riel
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