Messages in this thread | | | Date | Wed, 20 Mar 2013 07:34:02 +0800 | From | Ric Mason <> | Subject | Re: [PATCH v4 0/8] staging: zcache: Support zero-filled pages more efficiently |
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On 03/19/2013 05:25 PM, Wanpeng Li wrote: > Hi Greg, > > Since you have already merge 1/8, feel free to merge 2/8~8/8, I have already > rebased against staging-next. > > Changelog: > v3 -> v4: > * handle duplication in page_is_zero_filled, spotted by Bob > * fix zcache writeback in dubugfs > * fix pers_pageframes|_max isn't exported in debugfs > * fix static variable defined in debug.h but used in multiple C files > * rebase on Greg's staging-next > v2 -> v3: > * increment/decrement zcache_[eph|pers]_zpages for zero-filled pages, spotted by Dan > * replace "zero" or "zero page" by "zero_filled_page", spotted by Dan > v1 -> v2: > * avoid changing tmem.[ch] entirely, spotted by Dan. > * don't accumulate [eph|pers]pageframe and [eph|pers]zpages for > zero-filled pages, spotted by Dan > * cleanup TODO list > * add Dan Acked-by. > > Motivation: > > - Seth Jennings points out compress zero-filled pages with LZO(a lossless > data compression algorithm) will waste memory and result in fragmentation. > https://lkml.org/lkml/2012/8/14/347 > - Dan Magenheimer add "Support zero-filled pages more efficiently" feature > in zcache TODO list https://lkml.org/lkml/2013/2/13/503 > > Design: > > - For store page, capture zero-filled pages(evicted clean page cache pages and > swap pages), but don't compress them, set pampd which store zpage address to > 0x2(since 0x0 and 0x1 has already been ocuppied) to mark special zero-filled > case and take advantage of tmem infrastructure to transform handle-tuple(pool > id, object id, and an index) to a pampd. Twice compress zero-filled pages will > contribute to one zcache_[eph|pers]_pageframes count accumulated. > - For load page, traverse tmem hierachical to transform handle-tuple to pampd > and identify zero-filled case by pampd equal to 0x2 when filesystem reads > file pages or a page needs to be swapped in, then refill the page to zero > and return. > > Test: > > dd if=/dev/zero of=zerofile bs=1MB count=500 > vmtouch -t zerofile > vmtouch -e zerofile > > formula: > - fragmentation level = (zcache_[eph|pers]_pageframes * PAGE_SIZE - zcache_[eph|pers]_zbytes) > * 100 / (zcache_[eph|pers]_pageframes * PAGE_SIZE) > - memory zcache occupy = zcache_[eph|pers]_zbytes > > Result: > > without zero-filled awareness: > - fragmentation level: 98% > - memory zcache occupy: 238MB > with zero-filled awareness: > - fragmentation level: 0% > - memory zcache occupy: 0MB > > Wanpeng Li (8): > introduce zero filled pages handler > zero-filled pages awareness > handle zcache_[eph|pers]_pages for zero-filled page > fix pers_pageframes|_max aren't exported in debugfs > fix zcache writeback in debugfs > fix static variables are defined in debug.h but use in multiple C files > introduce zero-filled page stat count > clean TODO list
You can add Reviewed-by: Ric Mason <ric.masonn@gmail.com> to this patchset.
> > drivers/staging/zcache/TODO | 3 +- > drivers/staging/zcache/debug.c | 5 +- > drivers/staging/zcache/debug.h | 77 +++++++++++++--------- > drivers/staging/zcache/zcache-main.c | 147 ++++++++++++++++++++++++++++++---- > 4 files changed, 185 insertions(+), 47 deletions(-) >
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