From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Andi Kleen <andi@firstfloor.org>, "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, Miaohe Lin <linmiaohe@huawei.com>,
Naoya Horiguchi <nao.horiguchi@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>,
Rik van Riel <riel@redhat.com>,
Vlastimil Babka <vbabka@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <liam@infradead.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Brendan Jackman <jackmanb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>, Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Nico Pache <npache@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Harry Yoo <harry@kernel.org>, Hao Li <hao.li@linux.dev>,
Kiryl Shutsemau <kas@kernel.org>,
Byungchul Park <byungchul@sk.com>,
linux-mm@kvack.org, linux-cxl@vger.kernel.org
Subject: Re: [PATCH 0/2] mm: memory-failure: fix HWPoison flag race with non-atomic page flag ops
Date: Mon, 29 Jun 2026 19:04:25 +0200 [thread overview]
Message-ID: <20a5dfd4-b3c7-450a-8a70-08d0345aade4@kernel.org> (raw)
In-Reply-To: <akKjOG6iFhGNTFYC@firstfloor.org>
On 6/29/26 18:54, Andi Kleen wrote:
>> However, this was a basic test, when allocating 4k pages. With 2M hugepages:
>>
>> insns/iter cycles/iter
>> -------------------------------------------------------
>> base 20758 +/- 12.5 191208 +/-1946.6
>> rcu 20785 +/- 3.7 197108 +/- 132.1
>> atomic 20727 +/- 6.4 204591 +/- 160.2
>>
>> rcu vs base +27 (+0.13%) +5900 (+3.09%)
>> atomic vs base -31 (-0.15%) +13383 (+7.00%)
>>
>> and even with THP:
>>
>> insns/iter cycles/iter
>> -------------------------------------------------------
>> base 27220 +/- 2.8 192151 +/- 483.3
>> rcu 27248 +/- 30.1 194159 +/-2746.6
>> atomic 27186 +/- 3.2 200526 +/- 746.2
>>
>> rcu vs base +28 (+0.10%) +2008 (+1.04%)
>> atomic vs base -34 (-0.12%) +8374 (+4.36%)
>>
>>
>> needs more thought.
>
> Well the alternative is to not bother with RCU, but just wait a bit and
> check if the bit stuck and repeat if needed. While that could in theory
> livelock it is extremely unlikely (especially if you add a bit of randomization
> to the sleep)
We discussed that a bit already. Hypervisors make it fairly unpredictable how
long you would actually have to spin.
--
Cheers,
David
next prev parent reply other threads:[~2026-06-29 17:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-28 21:45 [PATCH 0/2] mm: memory-failure: fix HWPoison flag race with non-atomic page flag ops Michael S. Tsirkin
2026-06-28 21:45 ` [PATCH 1/2] mm: memory-failure: use RCU to fix HWPoison flag race Michael S. Tsirkin
2026-06-28 21:45 ` [PATCH 2/2] mm: wrap non-atomic page flag ops in RCU for HWPoison safety Michael S. Tsirkin
2026-06-29 2:11 ` [PATCH 0/2] mm: memory-failure: fix HWPoison flag race with non-atomic page flag ops Andi Kleen
2026-06-29 8:10 ` Michael S. Tsirkin
2026-06-29 8:21 ` David Hildenbrand (Arm)
2026-06-29 8:39 ` Michael S. Tsirkin
2026-06-29 16:54 ` Andi Kleen
2026-06-29 17:04 ` David Hildenbrand (Arm) [this message]
2026-06-29 6:49 ` David Hildenbrand (Arm)
2026-06-29 7:34 ` Michael S. Tsirkin
2026-06-29 13:05 ` David Hildenbrand (Arm)
2026-06-29 20:08 ` Michael S. Tsirkin
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