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From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: David Hildenbrand <david@redhat.com>,
	Alexander Duyck <alexander.duyck@gmail.com>,
	virtio-dev@lists.oasis-open.org,  kvm@vger.kernel.org,
	mst@redhat.com, catalin.marinas@arm.com,  dave.hansen@intel.com,
	linux-kernel@vger.kernel.org, willy@infradead.org,
	 linux-mm@kvack.org, akpm@linux-foundation.org, will@kernel.org,
	 linux-arm-kernel@lists.infradead.org, osalvador@suse.de,
	yang.zhang.wz@gmail.com,  pagupta@redhat.com,
	konrad.wilk@oracle.com, nitesh@redhat.com, riel@surriel.com,
	 lcapitulino@redhat.com, wei.w.wang@intel.com,
	aarcange@redhat.com,  ying.huang@intel.com, pbonzini@redhat.com,
	dan.j.williams@intel.com,  fengguang.wu@intel.com,
	kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling
Date: Tue, 10 Sep 2019 15:14:47 -0700	[thread overview]
Message-ID: <ac75ce0302faa234860a49cc965a6d342b3ca685.camel@linux.intel.com> (raw)
In-Reply-To: <20190910121130.GU2063@dhcp22.suse.cz>

On Tue, 2019-09-10 at 14:11 +0200, Michal Hocko wrote:
> On Mon 09-09-19 08:11:36, Alexander Duyck wrote:
> > On Mon, 2019-09-09 at 10:14 +0200, David Hildenbrand wrote:
> > > On 07.09.19 19:25, Alexander Duyck wrote:
> > > > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> > > > 
> > > > Change the logic used to generate randomness in the suffle path so that we
> > > > can avoid cache line bouncing. The previous logic was sharing the offset
> > > > and entropy word between all CPUs. As such this can result in cache line
> > > > bouncing and will ultimately hurt performance when enabled.
> > > 
> > > So, usually we perform such changes if there is real evidence. Do you
> > > have any such performance numbers to back your claims?
> > 
> > I'll have to go rerun the test to get the exact numbers. The reason this
> > came up is that my original test was spanning NUMA nodes and that made
> > this more expensive as a result since the memory was both not local to the
> > CPU and was being updated by multiple sockets.
> 
> What was the pattern of page freeing in your testing? I am wondering
> because order 0 pages should be prevailing and those usually go via pcp
> lists so they do not get shuffled unless the batch is full IIRC.

So I am pretty sure my previous data was faulty. One side effect of the
page reporting is that it was evicting pages out of the guest and when the
pages were faulted back in they were coming from local page pools. This
was throwing off my early numbers and making tests look better than they
should have for the reported case.

I had this patch previously merged with another one so I wasn't testing it
on its own, it was instead a part of a bigger set. Now that I have tried
testing it on its own I can see that it has no significant impact on
performance. With that being the case I will probably just drop it.



  reply	other threads:[~2019-09-10 22:14 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-07 17:25 [PATCH v9 0/8] stg mail -e --version=v9 \ Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling Alexander Duyck
2019-09-09  8:14   ` David Hildenbrand
2019-09-09 15:11     ` Alexander Duyck
2019-09-10 12:11       ` Michal Hocko
2019-09-10 22:14         ` Alexander Duyck [this message]
2019-09-10 22:11     ` Alexander Duyck
2019-09-09  9:07   ` Kirill A. Shutemov
2019-09-09 15:12     ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 2/8] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-09-09  8:19   ` David Hildenbrand
2019-09-09  9:47   ` Kirill A. Shutemov
2019-09-09 15:22     ` Alexander Duyck
2019-09-09 15:35       ` Kirill A. Shutemov
2019-09-09 15:37         ` Alexander Duyck
2019-09-09 16:43     ` Alexander Duyck
2019-09-09 17:00       ` Kirill A. Shutemov
2019-09-10 12:20   ` Michal Hocko
2019-09-10 14:48     ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 3/8] mm: Move set/get_pcppage_migratetype to mmzone.h Alexander Duyck
2019-09-09  8:22   ` David Hildenbrand
2019-09-09  9:56   ` Kirill A. Shutemov
2019-09-09 18:01     ` Alexander Duyck
2019-09-09 18:12       ` Alexander Duyck
2019-09-10 12:23   ` Michal Hocko
2019-09-10 14:46     ` Alexander Duyck
2019-09-10 17:45       ` Michal Hocko
2019-09-10 20:26         ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 4/8] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-09-10 12:27   ` Michal Hocko
2019-09-07 17:25 ` [PATCH v9 5/8] arm64: Move hugetlb related definitions out of pgtable.h to page-defs.h Alexander Duyck
2019-09-09  8:52   ` David Hildenbrand
2019-09-09 15:27     ` Alexander Duyck
2019-09-17 17:48   ` Will Deacon
2019-09-17 20:07     ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 6/8] mm: Introduce Reported pages Alexander Duyck
2019-09-09 14:42   ` Kirill A. Shutemov
2019-09-09 16:25     ` Alexander Duyck
2019-09-09 16:33       ` Kirill A. Shutemov
2019-09-07 17:26 ` [PATCH v9 7/8] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-09-09  8:59   ` David Hildenbrand
2019-09-09 15:31     ` Alexander Duyck
2019-09-07 17:26 ` [PATCH v9 8/8] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
2019-09-07 17:34 ` [PATCH v9 0/8] mm / virtio: Provide support for unused page reporting Alexander Duyck
2019-09-10 12:42 ` [PATCH v9 0/8] stg mail -e --version=v9 \ Michal Hocko
2019-09-10 14:42   ` Alexander Duyck
2019-09-10 14:47     ` Michal Hocko
2019-09-10 16:05       ` Alexander Duyck
2019-09-10 16:18         ` [virtio-dev] " Dr. David Alan Gilbert
2019-09-10 16:22           ` David Hildenbrand
2019-09-11  9:23             ` Michael S. Tsirkin
2019-09-11  9:50               ` David Hildenbrand
2019-09-10 17:52         ` Michal Hocko
2019-09-10 18:00           ` Michal Hocko
2019-09-10 20:37             ` Alexander Duyck
2019-09-10 21:23           ` Alexander Duyck
2019-09-11 11:36             ` Michal Hocko
2019-09-11 11:47               ` David Hildenbrand
2019-09-11 12:08               ` Michael S. Tsirkin
2019-09-11 12:19                 ` Michal Hocko
2019-09-11 12:25                   ` Michal Hocko
2019-09-11 12:42                     ` David Hildenbrand
2019-09-11 12:54                       ` Michal Hocko
2019-09-11 13:03                         ` David Hildenbrand
2019-09-11 13:20                           ` Michal Hocko
2019-09-11 13:51                             ` Michal Hocko
2019-09-11 16:09                               ` David Hildenbrand
2019-09-12  7:16                                 ` Michal Hocko
2019-09-12  7:47                                   ` David Hildenbrand
2019-09-12  9:26                                     ` Michal Hocko
2019-09-12 12:00                                     ` Nitesh Narayan Lal
2019-09-11 14:03                             ` Nitesh Narayan Lal
2019-09-11 16:02                             ` David Hildenbrand
2019-09-11 13:19                         ` Nitesh Narayan Lal
2019-09-11 12:55                       ` Nitesh Narayan Lal
2019-09-11 15:12               ` Alexander Duyck
2019-09-12  9:19                 ` Michal Hocko
2019-09-12 10:24                   ` Kirill A. Shutemov
2019-09-12 11:11                     ` Michal Hocko
2019-09-12 15:42                   ` Alexander Duyck
2019-09-12 16:35                   ` Mel Gorman
2019-09-12 17:48                     ` Alexander Duyck

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