From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>, Shaohua Li <shli@fb.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Kernel-team@fb.com, hughd@google.com, riel@redhat.com,
mgorman@techsingularity.net
Subject: Re: [PATCH V5 6/6] proc: show MADV_FREE pages info in smaps
Date: Wed, 8 Mar 2017 14:36:15 +0900 [thread overview]
Message-ID: <20170308053615.GC11206@bbox> (raw)
In-Reply-To: <20170307144338.023080a8cd600172f37dfe16@linux-foundation.org>
Hi Andrew,
On Tue, Mar 07, 2017 at 02:43:38PM -0800, Andrew Morton wrote:
> On Tue, 7 Mar 2017 11:05:45 +0100 Michal Hocko <mhocko@kernel.org> wrote:
>
> > On Fri 03-03-17 16:10:27, Andrew Morton wrote:
> > > On Thu, 2 Mar 2017 17:30:54 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > > > It's not that I think you're wrong: it *is* an implementation detail.
> > > > > But we take a bit of incoherency from batching all over the place, so
> > > > > it's a little odd to take a stand over this particular instance of it
> > > > > - whether demanding that it'd be fixed, or be documented, which would
> > > > > only suggest to users that this is special when it really isn't etc.
> > > >
> > > > I am not aware of other counter printed in smaps that would suffer from
> > > > the same problem, but I haven't checked too deeply so I might be wrong.
> > > >
> > > > Anyway it seems that I am alone in my position so I will not insist.
> > > > If we have any bug report then we can still fix it.
> > >
> > > A single lru_add_drain_all() right at the top level (in smaps_show()?)
> > > won't kill us
> >
> > I do not think we want to put lru_add_drain_all cost to a random
> > process reading /proc/<pid>/smaps.
>
> Why not? It's that process which is calling for the work to be done.
>
> > If anything the one which does the
> > madvise should be doing this.
>
> But it would be silly to do extra work in madvise() if nobody will be
> reading smaps for the next two months.
>
> How much work is it anyway? What would be the relative impact upon a
> smaps read?
I agree only if the draining guarantees all of mapped pages in the range
could be marked to lazyfree. However, it's not true because there are a
few of logics to skip the page marking in madvise_free_pte_range.
So, my conclusion is drainning helps a bit but not gaurantees.
In such case, IMHO, let's not do the effort to make better.
Thanks.
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prev parent reply other threads:[~2017-03-08 5:36 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-24 21:31 [PATCH V5 0/6] mm: fix some MADV_FREE issues Shaohua Li
2017-02-24 21:31 ` [PATCH V5 1/6] mm: delete unnecessary TTU_* flags Shaohua Li
2017-02-27 13:48 ` Michal Hocko
2017-02-24 21:31 ` [PATCH V5 2/6] mm: don't assume anonymous pages have SwapBacked flag Shaohua Li
2017-02-27 6:48 ` Hillf Danton
2017-02-27 14:35 ` Michal Hocko
2017-02-27 16:10 ` Shaohua Li
2017-02-27 16:28 ` Michal Hocko
2017-02-24 21:31 ` [PATCH V5 3/6] mm: move MADV_FREE pages into LRU_INACTIVE_FILE list Shaohua Li
2017-02-27 6:28 ` Minchan Kim
2017-02-27 16:13 ` Shaohua Li
2017-02-27 16:30 ` Michal Hocko
2017-02-28 2:53 ` Minchan Kim
2017-02-27 14:53 ` Michal Hocko
2017-02-27 17:15 ` Johannes Weiner
2017-02-28 3:19 ` Hillf Danton
2017-02-24 21:31 ` [PATCH V5 4/6] mm: reclaim MADV_FREE pages Shaohua Li
2017-02-27 6:33 ` Minchan Kim
2017-02-27 16:19 ` Shaohua Li
2017-02-27 16:32 ` Michal Hocko
2017-02-28 5:02 ` Minchan Kim
2017-02-27 15:05 ` Michal Hocko
2017-02-27 17:21 ` Johannes Weiner
2017-02-28 3:21 ` Hillf Danton
2017-02-24 21:31 ` [PATCH V5 5/6] mm: enable MADV_FREE for swapless system Shaohua Li
2017-02-27 15:06 ` Michal Hocko
2017-02-28 3:22 ` Hillf Danton
2017-02-28 5:02 ` Minchan Kim
2017-02-24 21:31 ` [PATCH V5 6/6] proc: show MADV_FREE pages info in smaps Shaohua Li
2017-02-27 15:06 ` Michal Hocko
2017-02-28 3:23 ` Hillf Danton
2017-03-01 13:36 ` Michal Hocko
2017-03-01 17:37 ` Shaohua Li
2017-03-01 17:49 ` Michal Hocko
2017-03-01 18:18 ` Shaohua Li
2017-03-01 18:31 ` Johannes Weiner
2017-03-01 18:57 ` Michal Hocko
2017-03-02 7:39 ` Minchan Kim
2017-03-02 14:01 ` Johannes Weiner
2017-03-02 16:30 ` Michal Hocko
2017-03-04 0:10 ` Andrew Morton
2017-03-07 10:05 ` Michal Hocko
2017-03-07 22:43 ` Andrew Morton
2017-03-08 5:36 ` Minchan Kim [this message]
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