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 1/4] readahead: state based method - stand-alone size limit code
Date: Tue, 30 May 2006 16:40:31 +0800 [thread overview]
Message-ID: <348978812.17342@ustc.edu.cn> (raw)
Message-ID: <20060530084702.611578500@localhost.localdomain> (raw)
In-Reply-To: 20060530084030.274375770@localhost.localdomain
[-- Attachment #1: readahead-method-stateful-fix-size-limit-sep.patch --]
[-- Type: text/plain, Size: 2594 bytes --]
Separate out the readahead/lookahead sizes limiting code,
and put them to stand-alone limit_rala() function.
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---
--- linux-2.6.17-rc4-mm3.orig/mm/readahead.c
+++ linux-2.6.17-rc4-mm3/mm/readahead.c
@@ -1009,10 +1009,8 @@ static int ra_dispatch(struct file_ra_st
* - @la_size stores the look-ahead size of previous request.
*/
static int adjust_rala(unsigned long ra_max,
- unsigned long *ra_size, unsigned long *la_size)
+ unsigned long *ra_size, unsigned long *la_size)
{
- unsigned long stream_shift = *la_size;
-
/*
* Substract the old look-ahead to get real safe size for the next
* read-ahead request.
@@ -1029,8 +1027,16 @@ static int adjust_rala(unsigned long ra_
*/
*la_size = *ra_size / LOOKAHEAD_RATIO;
+ return 1;
+}
+
+static void limit_rala(unsigned long ra_max, unsigned long la_old,
+ unsigned long *ra_size, unsigned long *la_size)
+{
+ unsigned long stream_shift;
+
/*
- * Apply upper limits.
+ * Apply basic upper limits.
*/
if (*ra_size > ra_max)
*ra_size = ra_max;
@@ -1041,11 +1047,9 @@ static int adjust_rala(unsigned long ra_
* Make sure stream_shift is not too small.
* (So that the next global_shift will not be too small.)
*/
- stream_shift += (*ra_size - *la_size);
+ stream_shift = la_old + (*ra_size - *la_size);
if (stream_shift < *ra_size / 4)
*la_size -= (*ra_size / 4 - stream_shift);
-
- return 1;
}
/*
@@ -1117,13 +1121,13 @@ state_based_readahead(struct address_spa
struct page *page, pgoff_t index,
unsigned long req_size, unsigned long ra_max)
{
- unsigned long ra_old;
- unsigned long ra_size;
- unsigned long la_size;
+ unsigned long ra_old, ra_size;
+ unsigned long la_old, la_size;
unsigned long remain_space;
unsigned long growth_limit;
- la_size = ra->readahead_index - index;
+ la_old = la_size = ra->readahead_index - index;
+ ra_old = ra_readahead_size(ra);
ra_size = compute_thrashing_threshold(ra, &remain_space);
if (page && remain_space <= la_size && la_size > 1) {
@@ -1131,7 +1135,6 @@ state_based_readahead(struct address_spa
return 0;
}
- ra_old = ra_readahead_size(ra);
growth_limit = req_size;
growth_limit += ra_max / 16;
growth_limit += (2 + readahead_ratio / 64) * ra_old;
@@ -1141,6 +1144,8 @@ state_based_readahead(struct address_spa
if (!adjust_rala(growth_limit, &ra_size, &la_size))
return 0;
+ limit_rala(growth_limit, la_old, &ra_size, &la_size);
+
ra_set_class(ra, RA_CLASS_STATE);
ra_set_index(ra, index, ra->readahead_index);
ra_set_size(ra, ra_size, la_size);
--
next prev parent reply other threads:[~2006-05-30 8:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-30 8:40 [patch 0/4] Adaptive readahead patchset V14 updates Wu Fengguang
2006-05-30 8:40 ` Wu Fengguang
2006-05-30 8:40 ` Wu Fengguang [this message]
2006-05-30 8:40 ` [patch 1/4] readahead: state based method - stand-alone size limit code Wu Fengguang
2006-05-30 8:40 ` [patch 3/4] readahead: context based method - fix *remain counting Wu Fengguang
2006-05-30 8:40 ` Wu Fengguang
2006-05-30 8:40 ` [patch 4/4] readahead: backward prefetching method - add use case comment Wu Fengguang
2006-05-30 8:40 ` Wu Fengguang
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