From: Shaohua Li <shli@fb.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
<Kernel-team@fb.com>, <mhocko@suse.com>, <minchan@kernel.org>,
<hughd@google.com>, <riel@redhat.com>,
<mgorman@techsingularity.net>, <akpm@linux-foundation.org>
Subject: Re: [PATCH V4 3/6] mm: move MADV_FREE pages into LRU_INACTIVE_FILE list
Date: Thu, 23 Feb 2017 11:04:46 -0800 [thread overview]
Message-ID: <20170223190446.GA32825@shli-mbp.local> (raw)
In-Reply-To: <20170223182206.GA5686@cmpxchg.org>
On Thu, Feb 23, 2017 at 01:22:06PM -0500, Johannes Weiner wrote:
> On Thu, Feb 23, 2017 at 08:26:03AM -0800, Shaohua Li wrote:
> > On Thu, Feb 23, 2017 at 10:58:27AM -0500, Johannes Weiner wrote:
> > > Hi Shaohua,
> > >
> > > On Wed, Feb 22, 2017 at 10:50:41AM -0800, Shaohua Li wrote:
> > > > @@ -268,6 +268,12 @@ static void __activate_page(struct page *page, struct lruvec *lruvec,
> > > > int lru = page_lru_base_type(page);
> > > >
> > > > del_page_from_lru_list(page, lruvec, lru);
> > > > + if (PageAnon(page) && !PageSwapBacked(page)) {
> > > > + SetPageSwapBacked(page);
> > > > + /* charge to anon scanned/rotated reclaim_stat */
> > > > + file = 0;
> > > > + lru = LRU_INACTIVE_ANON;
> > > > + }
> > >
> > > As per my previous feedback, please remove this. Write-after-free will
> > > be caught and handled in the reclaimer, read-after-free is a bug that
> > > really doesn't require optimizing page aging for. And we definitely
> > > shouldn't declare invalid data suddenly valid because it's being read.
> >
> > GUP could run into this. Don't we move the page because it's hot? I think it's
> > not just about page aging. If we leave the page there, page reclaim will just
> > waste time to reclaim the pages which should't be reclaimed.
>
> There is just no convincing justification to add this code, because it
> optimizes something that doesn't have a real world application. If we
> just delete this branch, for all intents and purposes the outcome will
> be perfectly acceptable.
Ok, looks you want to ignore all corner cases, the gup case is one and the
unmap failure and mlock case we discussed before are another. I don't disagree
with the intention, but I had the feeling those code will eventually come back.
Anyway, I'll delete this code in next post.
Thanks,
Shaohua
next prev parent reply other threads:[~2017-02-23 19:28 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-22 18:50 [PATCH V4 0/6] mm: fix some MADV_FREE issues Shaohua Li
2017-02-22 18:50 ` [PATCH V4 1/6] mm: delete unnecessary TTU_* flags Shaohua Li
2017-02-23 15:35 ` Johannes Weiner
2017-02-24 1:25 ` Minchan Kim
2017-02-24 3:29 ` Hillf Danton
2017-02-22 18:50 ` [PATCH V4 2/6] mm: don't assume anonymous pages have SwapBacked flag Shaohua Li
2017-02-22 18:50 ` [PATCH V4 3/6] mm: move MADV_FREE pages into LRU_INACTIVE_FILE list Shaohua Li
2017-02-23 15:58 ` Johannes Weiner
2017-02-23 16:26 ` Shaohua Li
2017-02-23 18:22 ` Johannes Weiner
2017-02-23 19:04 ` Shaohua Li [this message]
2017-02-24 1:49 ` Minchan Kim
2017-02-24 6:15 ` Shaohua Li
2017-02-24 23:37 ` Minchan Kim
2017-02-22 18:50 ` [PATCH V4 4/6] mm: reclaim MADV_FREE pages Shaohua Li
2017-02-23 16:13 ` Johannes Weiner
2017-02-23 17:19 ` Shaohua Li
2017-02-24 2:12 ` Minchan Kim
2017-02-24 6:14 ` Shaohua Li
2017-02-24 15:36 ` Johannes Weiner
2017-02-24 23:26 ` Minchan Kim
2017-02-22 18:50 ` [PATCH V4 5/6] mm: enable MADV_FREE for swapless system Shaohua Li
2017-02-22 18:50 ` [PATCH V4 6/6] proc: show MADV_FREE pages info in smaps Shaohua Li
2017-02-23 16:16 ` Johannes Weiner
2017-02-24 2:13 ` Minchan Kim
2017-02-24 17:08 ` Dave Hansen
2017-02-24 21:47 ` Shaohua Li
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