From: Andrea Arcangeli <aarcange@redhat.com>
To: Nai Xia <nai.xia@gmail.com>
Cc: Rik van Riel <riel@redhat.com>,
Izik Eidus <izik.eidus@ravellosystems.com>,
Avi Kivity <avi@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Chris Wright <chrisw@sous-sol.org>, linux-mm <linux-mm@kvack.org>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
kvm <kvm@vger.kernel.org>
Subject: Re: [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spte and mmu notifier to help KSM dirty bit tracking
Date: Thu, 23 Jun 2011 01:25:32 +0200 [thread overview]
Message-ID: <20110622232532.GA20843@redhat.com> (raw)
In-Reply-To: <BANLkTikidXPzyxySbmrXK=EUXOzqMtm-0g@mail.gmail.com>
On Thu, Jun 23, 2011 at 07:13:54AM +0800, Nai Xia wrote:
> I agree on this point. Dirty bit , young bit, is by no means accurate. Even
> on 4kB pages, there is always a chance that the pte are dirty but the contents
> are actually the same. Yeah, the whole optimization contains trade-offs and
Just a side note: the fact the dirty bit would be set even when the
data is the same is actually a pros, not a cons. If the content is the
same but the page was written to, it'd trigger a copy on write short
after merging the page rendering the whole exercise wasteful. The
cksum plays a double role, it both "stabilizes" the unstable tree, so
there's less chance of bad lookups, but it also avoids us to merge
stuff that is written to frequently triggering copy on writes, and the
dirty bit would also catch overwrites with the same data, something
the cksum can't do.
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next prev parent reply other threads:[~2011-06-22 23:25 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-21 12:55 [PATCH 0/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Nai Xia
2011-06-21 13:26 ` [PATCH 1/2 " Nai Xia
2011-06-21 21:42 ` Chris Wright
2011-06-22 0:02 ` Nai Xia
2011-06-22 0:42 ` Chris Wright
2011-06-21 13:32 ` [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spte and mmu notifier to help KSM dirty bit tracking Nai Xia
2011-06-22 0:21 ` Chris Wright
2011-06-22 4:43 ` Nai Xia
2011-06-22 6:15 ` Izik Eidus
2011-06-22 6:38 ` Nai Xia
2011-06-22 15:46 ` Chris Wright
2011-06-22 10:43 ` Avi Kivity
2011-06-22 11:05 ` Izik Eidus
2011-06-22 11:10 ` Avi Kivity
2011-06-22 11:19 ` Izik Eidus
2011-06-22 11:24 ` Avi Kivity
2011-06-22 11:28 ` Avi Kivity
2011-06-22 11:31 ` Avi Kivity
2011-06-22 11:33 ` Nai Xia
2011-06-22 11:39 ` Izik Eidus
2011-06-22 15:39 ` Rik van Riel
2011-06-22 16:55 ` Andrea Arcangeli
2011-06-22 23:37 ` Nai Xia
2011-06-22 23:59 ` Andrea Arcangeli
2011-06-23 0:31 ` Nai Xia
2011-06-23 0:44 ` Andrea Arcangeli
2011-06-23 1:36 ` Nai Xia
2011-06-23 0:00 ` Rik van Riel
2011-06-23 0:42 ` Nai Xia
2011-06-22 23:13 ` Nai Xia
2011-06-22 23:25 ` Andrea Arcangeli [this message]
2011-06-23 1:30 ` Nai Xia
2011-06-22 23:28 ` Rik van Riel
2011-06-23 0:52 ` Nai Xia
2011-06-22 11:24 ` Nai Xia
2011-06-22 15:03 ` Andrea Arcangeli
2011-06-22 15:19 ` Izik Eidus
2011-06-22 23:19 ` Nai Xia
2011-06-22 23:44 ` Andrea Arcangeli
2011-06-23 0:14 ` Nai Xia
2011-06-22 23:42 ` Nai Xia
2011-06-21 13:36 ` [PATCH 2/2 V2] ksm: take dirty bit as reference to avoid volatile pages scanning Nai Xia
2011-06-21 22:38 ` Chris Wright
2011-06-22 0:04 ` Nai Xia
2011-06-22 0:35 ` Chris Wright
2011-06-22 4:47 ` Nai Xia
2011-06-22 10:55 ` Nai Xia
2011-06-22 0:46 ` [PATCH 0/2 " Chris Wright
2011-06-22 4:15 ` Nai Xia
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