From: Wu Fengguang <wfg@mail.ustc.edu.cn>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org, Wu Fengguang <wfg@mail.ustc.edu.cn>
Subject: [PATCH 1/6] readahead: context based method - slow start
Date: Sun, 25 Jun 2006 21:07:05 +0800 [thread overview]
Message-ID: <351240952.23410@ustc.edu.cn> (raw)
Message-ID: <20060625130921.549904049@localhost.localdomain> (raw)
In-Reply-To: 20060625130704.464870100@localhost.localdomain
[-- Attachment #1: readahead-context-fix.patch --]
[-- Type: text/plain, Size: 716 bytes --]
The context method will lead to noticable overhead on sparse random reads.
Having the readahead window to start slowly makes it much better.
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---
--- linux-2.6.17-mm2.orig/mm/readahead.c
+++ linux-2.6.17-mm2/mm/readahead.c
@@ -1548,6 +1548,11 @@ try_context_based_readahead(struct addre
return -1;
} else if (prev_page || probe_page(mapping, index - 1)) {
ra_index = index;
+ /*
+ * Slow start of readahead window.
+ * It helps avoid most readahead miss on sparse random reads.
+ */
+ ra_min = readahead_hit_rate;
} else if (readahead_hit_rate > 1) {
ra_index = find_segtail_backward(mapping, index,
readahead_hit_rate + ra_min);
--
next prev parent reply other threads:[~2006-06-25 13:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20060625130704.464870100@localhost.localdomain>
2006-06-25 13:07 ` [PATCH 0/6] Adaptive readahead updates 3 Wu Fengguang
[not found] ` <20060625130921.549904049@localhost.localdomain>
2006-06-25 13:07 ` Wu Fengguang [this message]
[not found] ` <20060626023529.GB6120@mail.ustc.edu.cn>
2006-06-26 2:35 ` [updated PATCH 1/6] readahead: context based method - slow start Wu Fengguang
[not found] ` <20060625130921.987235199@localhost.localdomain>
2006-06-25 13:07 ` [PATCH 2/6] readahead: backward prefetching method fix Wu Fengguang
[not found] ` <20060625130922.216691316@localhost.localdomain>
2006-06-25 13:07 ` [PATCH 3/6] readahead: kconfig option READAHEAD_ALLOW_OVERHEADS Wu Fengguang
[not found] ` <20060625130922.816467605@localhost.localdomain>
2006-06-25 13:07 ` [PATCH 5/6] readahead: kconfig option READAHEAD_HIT_FEEDBACK Wu Fengguang
[not found] ` <20060625130923.154258797@localhost.localdomain>
2006-06-25 13:07 ` [PATCH 6/6] readahead: remove the size limit of max_sectors_kb on read_ahead_kb Wu Fengguang
[not found] ` <20060626015256.GA6120@mail.ustc.edu.cn>
2006-06-26 1:52 ` [PATCH 0/6] Adaptive readahead updates 3 Wu Fengguang
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