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>,
Rik van Riel <riel@redhat.com>,
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 16/16] readahead: pagecache context based mmap read-around
Date: Mon, 01 Mar 2010 13:27:07 +0800 [thread overview]
Message-ID: <20100301053622.514378154@intel.com> (raw)
In-Reply-To: 20100301052651.857984880@intel.com
[-- Attachment #1: readahead-mmap-around-context.patch --]
[-- Type: text/plain, Size: 1581 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>
Acked-by: Rik van Riel <riel@redhat.com>
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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prev parent reply other threads:[~2010-03-01 5:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-01 5:26 [PATCH 00/16] [PATCH 00/15] 512K readahead size with thrashing safe readahead v3 Wu Fengguang
2010-03-01 5:26 ` [PATCH 01/16] readahead: limit readahead size for small devices Wu Fengguang
2010-03-01 5:26 ` [PATCH 02/16] readahead: retain inactive lru pages to be accessed soon Wu Fengguang
2010-03-01 5:26 ` [PATCH 03/16] readahead: bump up the default readahead size Wu Fengguang
2010-03-01 5:26 ` [PATCH 04/16] readahead: make default readahead size a kernel parameter Wu Fengguang
2010-03-01 5:26 ` [PATCH 05/16] readahead: limit read-ahead size for small memory systems Wu Fengguang
2010-03-01 5:26 ` [PATCH 06/16] readahead: add notes on readahead size Wu Fengguang
2010-03-01 5:26 ` [PATCH 07/16] readahead: replace ra->mmap_miss with ra->ra_flags Wu Fengguang
2010-03-01 5:26 ` [PATCH 08/16] readahead: thrashing safe context readahead Wu Fengguang
2010-03-01 5:27 ` [PATCH 09/16] readahead: record readahead patterns Wu Fengguang
2010-03-01 5:27 ` [PATCH 10/16] readahead: add tracing event Wu Fengguang
2010-03-01 5:27 ` [PATCH 11/16] readahead: add /debug/readahead/stats Wu Fengguang
2010-03-01 5:27 ` [PATCH 12/16] readahead: dont do start-of-file readahead after lseek() Wu Fengguang
2010-03-01 5:27 ` [PATCH 13/16] radixtree: introduce radix_tree_lookup_leaf_node() Wu Fengguang
2010-03-01 5:27 ` [PATCH 14/16] radixtree: speed up the search for hole Wu Fengguang
2010-03-01 5:27 ` [PATCH 15/16] readahead: reduce MMAP_LOTSAMISS for mmap read-around Wu Fengguang
2010-03-01 5:27 ` Wu Fengguang [this message]
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