From: Chris Mason <clm@fb.com>
To: Dave Chinner <david@fromorbit.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
Roman Gushchin <guro@fb.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"mhocko@kernel.org" <mhocko@kernel.org>,
"vdavydov.dev@gmail.com" <vdavydov.dev@gmail.com>
Subject: Re: [PATCH 1/2] Revert "mm: don't reclaim inodes with many attached pages"
Date: Thu, 31 Jan 2019 15:48:11 +0000 [thread overview]
Message-ID: <E8895615-9DDA-4FC5-A3AB-1BE593138A89@fb.com> (raw)
In-Reply-To: <20190131013403.GI4205@dastard>
On 30 Jan 2019, at 20:34, Dave Chinner wrote:
> On Wed, Jan 30, 2019 at 12:21:07PM +0000, Chris Mason wrote:
>>
>>
>> On 29 Jan 2019, at 23:17, Dave Chinner wrote:
>>
>>> From: Dave Chinner <dchinner@redhat.com>
>>>
>>> This reverts commit a76cf1a474d7dbcd9336b5f5afb0162baa142cf0.
>>>
>>> This change causes serious changes to page cache and inode cache
>>> behaviour and balance, resulting in major performance regressions
>>> when combining worklaods such as large file copies and kernel
>>> compiles.
>>>
>>> https://bugzilla.kernel.org/show_bug.cgi?id=202441
>>
>> I'm a little confused by the latest comment in the bz:
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=202441#c24
>
> Which says the first patch that changed the shrinker behaviour is
> the underlying cause of the regression.
>
>> Are these reverts sufficient?
>
> I think so.
Based on the latest comment:
"If I had been less strict in my testing I probably would have
discovered that the problem was present earlier than 4.19.3. Mr Gushins
commit made it more visible.
I'm going back to work after two days off, so I might not be able to
respond inside your working hours, but I'll keep checking in on this as
I get a chance."
I don't think the reverts are sufficient.
>
>> Roman beat me to suggesting Rik's followup. We hit a different
>> problem
>> in prod with small slabs, and have a lot of instrumentation on Rik's
>> code helping.
>
> I think that's just another nasty, expedient hack that doesn't solve
> the underlying problem. Solving the underlying problem does not
> require changing core reclaim algorithms and upsetting a page
> reclaim/shrinker balance that has been stable and worked well for
> just about everyone for years.
>
Things are definitely breaking down in non-specialized workloads, and
have been for a long time.
-chris
next prev parent reply other threads:[~2019-01-31 15:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-30 4:17 [PATCH 0/2] [REGRESSION v4.19-20] mm: shrinkers are now way too aggressive Dave Chinner
2019-01-30 4:17 ` [PATCH 1/2] Revert "mm: don't reclaim inodes with many attached pages" Dave Chinner
2019-01-30 12:21 ` Chris Mason
2019-01-31 1:34 ` Dave Chinner
2019-01-31 9:10 ` Michal Hocko
2019-01-31 18:57 ` Roman Gushchin
2019-01-31 22:19 ` Dave Chinner
2019-02-04 21:47 ` Dave Chinner
2019-02-07 10:27 ` Jan Kara
2019-02-08 5:37 ` Andrew Morton
2019-02-08 9:55 ` Jan Kara
2019-02-08 12:50 ` Jan Kara
2019-02-08 22:49 ` Andrew Morton
2019-02-09 3:42 ` Roman Gushchin
2019-02-08 21:25 ` Dave Chinner
2019-02-11 15:34 ` Wolfgang Walter
2019-01-31 15:48 ` Chris Mason [this message]
2019-02-01 23:39 ` Dave Chinner
2019-01-30 4:17 ` [PATCH 2/2] Revert "mm: slowly shrink slabs with a relatively small number of objects" Dave Chinner
2019-01-30 5:48 ` [PATCH 0/2] [REGRESSION v4.19-20] mm: shrinkers are now way too aggressive Roman Gushchin
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