Messages in this thread |  | | | Date | Fri, 26 Aug 2011 08:24:47 -0500 | | From | Seth Jennings <> | | Subject | Re: cleancache can lead to serious performance degradation |
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On 08/25/2011 11:56 AM, Dan Magenheimer wrote:
> Third, zcache is relatively new and can certainly benefit from > the input of other developers. The lzo1x compression in the kernel > is fairly slow; Seth Jennings (cc'ed) is looking into alternate > compression technologies. Perhaps there is a better compression > choice more suitable for older-slower processors, probably with a > poorer compression ratio. Further, zcache currently does compression > and decompression with interrupts disabled, which may be a > significant factor in the slowdowns you've observed. This should > be fixable.
This was something I've meaning to ask about. Why are compression and decompression done with interrupts disabled? What would need to change so that we don't have to disable interrupts?
<cut> >>> I guess that possible workaround could be to implement some kind of >>> compression throttling valve for cleancache/zcache: >>> >>> - if there's available CPU time (idle cycles or so), then compress >>> (maybe even with low CPU scheduler priority); > > Agreed, and this low-priority kernel thread ideally would also > solve the "compress while irqs disabled" problem!
-- Seth
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