Messages in this thread | | | Date | Thu, 30 Oct 2003 13:44:07 -0800 | From | Andrew Morton <> | Subject | Re: READAHEAD |
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age <ahuisman@cistron.nl> wrote: > > I have a problem which i don`t understand and i hope that you > will and can help me. The problem is that i experience strange disk > read performance. I have to set hdparm -m16 -u1 -c1 -d1 -a4096 /dev/hde > to get timing buffered disk reads of 56 MB/SEC. > When i disable readahead i get 17 MB/SEC > When i enable readahead with -a8 i get 17 MB/SEC > When i enable readahead with -a16 i get 24,5 MB/SEC > When i enable readahead with -a32 i get 30,5 MB/SEC > When i enable readahead with -a64 i get 35 MB/SEC > When i enable readahead with -a128 i get 39 MB/SEC > When i enable readahead with -a256 i get 39 MB/SEC > When i enable readahead with -a512 i get 41 MB/SEC > When i enable readahead with -a1024 i get 50 MB/SEC > When i enable readahead with -a2048 i get 50 MB/SEC > When i enable readahead with -a4096 i get 56 MB/SEC > With -a8192,-a16384 and -a32768 i get also 56MB/SEC > > Before, i never had to set readahead so high > Please could you tell me, what is going on here ?
Lots of people have been reporting this. It's rather weird.
Is the same effect observable when reading a large file, or is it only observable via `hdparm -t'?
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