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    SubjectRe: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock
    * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-03-18 13:21:14]:

    > On Thu, 18 Mar 2010 09:49:44 +0530
    > Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
    >
    > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-03-18 08:54:11]:
    > >
    > > > On Wed, 17 Mar 2010 17:28:55 +0530
    > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
    > > >
    > > > > * Andrea Righi <arighi@develer.com> [2010-03-15 00:26:38]:
    > > > >
    > > > > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > > > > >
    > > > > > Now, file-mapped is maintaiend. But more generic update function
    > > > > > will be needed for dirty page accounting.
    > > > > >
    > > > > > For accountig page status, we have to guarantee lock_page_cgroup()
    > > > > > will be never called under tree_lock held.
    > > > > > To guarantee that, we use trylock at updating status.
    > > > > > By this, we do fuzzy accounting, but in almost all case, it's correct.
    > > > > >
    > > > >
    > > > > I don't like this at all, but in almost all cases is not acceptable
    > > > > for statistics, since decisions will be made on them and having them
    > > > > incorrect is really bad. Could we do a form of deferred statistics and
    > > > > fix this.
    > > > >
    > > >
    > > > plz show your implementation which has no performance regresssion.
    > > > For me, I don't neee file_mapped accounting, at all. If we can remove that,
    > > > we can add simple migration lock.
    > >
    > > That doesn't matter, if you need it, I think the larger user base
    > > matters. Unmapped and mapped page cache is critical and I use it
    > > almost daily.
    > >
    > > > file_mapped is a feattue you added. please improve it.
    > > >
    > >
    > > I will, but please don't break it silently
    > >
    > I never do silently. All e-mails are open.
    >

    No, I meant it from the Documentation update perspective. The end user
    will be confused when looking at stats without proper documentation.

    --
    Three Cheers,
    Balbir


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