Messages in this thread | | | Date | Wed, 9 Dec 2009 09:43:31 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 2/9] ksm: let shared pages be swappable |
| |
On Fri, 4 Dec 2009 09:16:40 -0800 Chris Wright <chrisw@redhat.com> wrote:
> * KAMEZAWA Hiroyuki (kamezawa.hiroyu@jp.fujitsu.com) wrote: > > KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote: > > > Windows kernel have zero page thread and it clear the pages in free list > > > periodically. because many windows subsystem prerefer zero filled page. > > > hen, if we use windows guest, zero filled page have plenty mapcount rather > > > than other typical sharing pages, I guess. > > > > > > So, can we mark as unevictable to zero filled ksm page? > > That's why I mentioned the page of zeroes as the prime example of > something with a high mapcount that shouldn't really ever be evicted. > > > Hmm, can't we use ZERO_PAGE we have now ? > > If do so, > > - no mapcount check > > - never on LRU > > - don't have to maintain shared information because ZERO_PAGE itself has > > copy-on-write nature. > > It's a somewhat special case, but wouldn't it be useful to have a generic > method to recognize this kind of sharing since it's a generic issue? >
I just remembered that why ZERO_PAGE was removed (in past). It was becasue cache-line ping-pong at fork beacause of page->mapcount. And KSM introduces zero-pages which have mapcount again. If no problems in realitsitc usage of KVM, ignore me.
Thanks, -Kame
| |