From: Michal Hocko <mhocko@suse.com>
To: Liang Li <liliang324@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Dan Williams <dan.j.williams@intel.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
David Hildenbrand <david@redhat.com>,
Jason Wang <jasowang@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
Liang Li <liliangleo@didiglobal.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [RFC v2 PATCH 0/4] speed up page allocation for __GFP_ZERO
Date: Mon, 4 Jan 2021 13:51:22 +0100 [thread overview]
Message-ID: <20210104125122.GD13207@dhcp22.suse.cz> (raw)
In-Reply-To: <CA+2MQi8GMLfSFN30G8EEeXXsC5M+Et2oRMnynUp==eRbY0Z2Wg@mail.gmail.com>
On Tue 22-12-20 22:42:13, Liang Li wrote:
> > > =====================================================
> > > QEMU use 4K pages, THP is off
> > > round1 round2 round3
> > > w/o this patch: 23.5s 24.7s 24.6s
> > > w/ this patch: 10.2s 10.3s 11.2s
> > >
> > > QEMU use 4K pages, THP is on
> > > round1 round2 round3
> > > w/o this patch: 17.9s 14.8s 14.9s
> > > w/ this patch: 1.9s 1.8s 1.9s
> > > =====================================================
> >
> > The cost of zeroing pages has to be paid somewhere. You've successfully
> > moved it out of this path that you can measure. So now you've put it
> > somewhere that you're not measuring. Why is this a win?
>
> Win or not depends on its effect. For our case, it solves the issue
> that we faced, so it can be thought as a win for us. If others don't
> have the issue we faced, the result will be different, maybe they will
> be affected by the side effect of this feature. I think this is your
> concern behind the question. right? I will try to do more tests and
> provide more benchmark performance data.
Yes, zeroying memory does have a noticeable overhead but we cannot
simply allow tasks to spil over this overhead to all other users by
default. So if anything this would need to be an opt-in feature
configurable by administrator.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-01-04 12:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-21 16:25 [RFC v2 PATCH 0/4] speed up page allocation for __GFP_ZERO Liang Li
2020-12-22 8:47 ` David Hildenbrand
2020-12-22 11:31 ` Liang Li
2020-12-22 11:57 ` David Hildenbrand
2020-12-22 14:00 ` Liang Li
2020-12-23 8:41 ` David Hildenbrand
2020-12-23 12:11 ` Liang Li
2021-01-04 20:18 ` David Hildenbrand
2021-01-05 2:14 ` Liang Li
2021-01-05 9:39 ` David Hildenbrand
2021-01-05 10:22 ` Liang Li
2021-01-05 10:27 ` David Hildenbrand
2020-12-22 12:23 ` Matthew Wilcox
2020-12-22 14:42 ` Liang Li
2021-01-04 12:51 ` Michal Hocko [this message]
2021-01-04 13:45 ` Liang Li
2020-12-22 17:11 ` Daniel Jordan
2020-12-22 19:13 ` Alexander Duyck
2021-01-04 12:55 ` Michal Hocko
2021-01-04 14:07 ` Liang Li
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