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| author | Steven Pratt <slpratt@austin.ibm.com> | 2006-03-22 00:08:48 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-22 07:54:03 -0800 |
| commit | aed75ff3caafce404d9be7f0c088716375be5279 (patch) | |
| tree | 15e7165969ff533b73e29a4ee0d4b7c889ef1d29 | |
| parent | a564da3964db3256069190c2ae95069143ac37fb (diff) | |
| download | linux-aed75ff3caafce404d9be7f0c088716375be5279.tar.bz2 | |
[PATCH] readahead: fix initial window size calculation
The current current get_init_ra_size is not optimal across different IO
sizes and max_readahead values. Here is a quick summary of sizes computed
under current design and under the attached patch. All of these assume 1st
IO at offset 0, or 1st detected sequential IO.
32k max, 4k request
old new
-----------------
8k 8k
16k 16k
32k 32k
128k max, 4k request
old new
-----------------
32k 16k
64k 32k
128k 64k
128k 128k
128k max, 32k request
old new
-----------------
32k 64k <-----
64k 128k
128k 128k
512k max, 4k request
old new
-----------------
4k 32k <----
16k 64k
64k 128k
128k 256k
512k 512k
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Steven Pratt <slpratt@austin.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | mm/readahead.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/readahead.c b/mm/readahead.c index 57557e294987..301b36c4a0ce 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -83,10 +83,10 @@ static unsigned long get_init_ra_size(unsigned long size, unsigned long max) { unsigned long newsize = roundup_pow_of_two(size); - if (newsize <= max / 64) - newsize = newsize * newsize; + if (newsize <= max / 32) + newsize = newsize * 4; else if (newsize <= max / 4) - newsize = max / 4; + newsize = newsize * 2; else newsize = max; return newsize; |