Messages in this thread | | | Date | Sat, 19 Apr 2003 09:25:22 +1000 | From | Nick Piggin <> | Subject | Re: 2.5.67-mm4 |
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Toon van der Pas wrote:
>On Fri, Apr 18, 2003 at 01:45:36AM -0700, Andrew Morton wrote: > >>ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.5/2.5.67/2.5.67-mm4/ >> >>. A bunch of anticipatory scheduler patches. >> >> For the first time ever, AS is working well with both IDE and SCSI >> under all the usual tests. >> >> It works just fine on SCSI with zero TCQ tags, and with four TCQ tags. >> At eight tags, read-vs-write performace is starting to measurably drop off. >> At 32 tags it is about 2000x slower than at zero or four tags. >> >> My recommendation, as always, is to disable SCSI TCQ completely. If you >> really must, set it to four tags. >> > >What about drivers that bypass de SCSI layer? >I administer a server with a Mylex RAID controller (DAC960)... > I'd say they will show the same behaviour. As far as we can tell its an interaction between badly behaving TCQ disks (those which allow lots of writes to bypass a read), and the anticipatory scheduler. We will be working on fixing this so those inclined can use huge numbers of outstanding tags without things going too haywire.
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