From: David Rientjes <rientjes@google.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Wei Yang <richardw.yang@linux.intel.com>,
hannes@cmpxchg.org, vdavydov.dev@gmail.com,
akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
yang.shi@linux.alibaba.com, cgroups@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
alexander.duyck@gmail.com, stable@vger.kernel.org
Subject: Re: [Patch v3] mm: thp: grab the lock before manipulation defer list
Date: Fri, 17 Jan 2020 01:32:58 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.21.2001170132090.20618@chino.kir.corp.google.com> (raw)
In-Reply-To: <b67fe2bb-e7a6-29fe-925e-dd1ae176cc4b@virtuozzo.com>
On Fri, 17 Jan 2020, Kirill Tkhai wrote:
> >> I think that's a good point, especially considering that the current code
> >> appears to unconditionally place any compound page on the deferred split
> >> queue of the destination memcg. The correct list that it should appear
> >> on, I believe, depends on whether the pmd has been split for the process
> >> being moved: note the MC_TARGET_PAGE caveat in
> >> mem_cgroup_move_charge_pte_range() that does not move the charge for
> >> compound pages with split pmds. So when mem_cgroup_move_account() is
> >> called with compound == true, we're moving the charge of the entire
> >> compound page: why would it appear on that memcg's deferred split queue?
> >
> > I believe Kirill asked how do we know that the page should be actually
> > added to the deferred list just from the list_empty check. In other
> > words what if the page hasn't been split at all?
>
> Yes, I'm talking about this. Function mem_cgroup_move_account() adds every
> huge page to the deferred list, while we need to do that only for pages,
> which are queued for splitting...
>
Yup, and that appears broken before Wei's patch. Since we only migrate
charges of entire compound pages (we have a mapping pmd, the underlying
page cannot be split), it should not appear on the deferred split queue
for any memcg, right?
next prev parent reply other threads:[~2020-01-17 9:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 1:31 Wei Yang
2020-01-16 9:35 ` Kirill Tkhai
2020-01-16 22:01 ` David Rientjes
2020-01-17 0:47 ` Wei Yang
2020-01-17 9:10 ` Michal Hocko
2020-01-17 9:26 ` Kirill Tkhai
2020-01-17 9:32 ` David Rientjes [this message]
2020-01-17 9:42 ` Kirill Tkhai
2020-01-17 11:59 ` Michal Hocko
2020-01-17 9:31 ` David Rientjes
2020-01-17 15:38 ` Kirill A. Shutemov
2020-01-17 19:11 ` David Rientjes
2020-01-17 19:17 ` Yang Shi
2020-01-17 22:18 ` Wei Yang
2020-01-17 22:57 ` Kirill A. Shutemov
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