Re: Severe I/O performance regression 2.6.6 to 2.6.7 or 2.6.8-rc3

[William Lee Irwin III]

On Thu, Aug 05, 2004 at 12:02:09PM -0500, Mr. Berkley Shands wrote:
> Two severe disk read bugs:
> In a nutshell (see attached for gory details). Moving from 2.6.6 to 
> 2.6.7 dropped multi-threaded RAID0
> read performance from 429MB/Sec to 81MB/Sec. Single threaded reads 
> improved  368MB/Sec to 418MB/Sec.
> The code in drivers/md has no effect on this problem. Clearly this is a 
> thread access issue. Redhat ES3.0
> on x86_64 or i686.  The underlying hardware is capable of 955MB/Sec disk 
> reads off 28 drives,
> 541MB/Sec off 14 drives. Tuning I/O block size (11KB to 239KB) and 
> BLKRASET size (448 to 1024 or more)
> helps a little. System idle goes from 0% to 50% (2.6.6 to 2.6.8-rc3).

By any chance could you do binary search on the bk snapshots between
2.6.6 and 2.6.7?


-- wli
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