On Wed, Apr 03, 2013 at 06:16:20PM +0800, Wanpeng Li wrote: >Changelog: > v5 -> v6: > * shove variables in debug.c and in debug.h just have an extern, spotted by Konrad > * update patch description, spotted by Konrad > v4 -> v5: > * fix compile error, reported by Fengguang, Geert > * add check for !is_ephemeral(pool), spotted by Bob > 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. > Hi Dan, Some issues against Ramster: - Ramster who takes advantage of zcache also should support zero-filled pages more efficiently, correct? It doesn't handle zero-filled pages well currently. - Ramster DebugFS counters are exported in /sys/kernel/mm/, but zcache/frontswap/cleancache all are exported in /sys/kernel/debug/, should we unify them? - If ramster also should move DebugFS counters to a single file like zcache do? If you confirm these issues are make sense to fix, I will start coding. ;-) Regards, Wanpeng Li >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 (3): > staging: zcache: fix static variables defined in debug.h but used in > mutiple C files > staging: zcache: introduce zero-filled page stat count > staging: zcache: clean TODO list > > drivers/staging/zcache/TODO | 3 +- > drivers/staging/zcache/debug.c | 35 +++++++++++++++ > drivers/staging/zcache/debug.h | 79 ++++++++++++++++++++------------- > drivers/staging/zcache/zcache-main.c | 4 ++ > 4 files changed, 88 insertions(+), 33 deletions(-) > >-- >1.7.5.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>