Cached file read performance
markir at paradise.net.nz
Fri Dec 22 17:00:45 PST 2006
Bruce Evans wrote:
> None was attached.
(meaning the c prog yes?) I notice that it is stripped out from the web
archive... so here's a link:
>> - ufs2 32k blocksize, 4K fragments
> Try using an unpessimized block size. Block sizes larger than BKVASIZE
> (default 16K) fragment the buffer cache virtual memory.
Right - I should have said, I saw a comment to that effect in
src/sys/sys/param.h, and so I tested with 8K, 16K too, interestingly on
my system 32K seemed to be faster, even for the bigger files (of course
- hard to know if it was really significant...).
> However, I
> couldn't see much difference between block sizes of 16, 32 and 64K for
> a small (32MB) md-malloced file system with a simple test program.
> All versions got nearly 1/4 of bandwidth of main memory (800MB/S +-10%
> an an AthlonXP with ~PC3200 memory).
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