From: "Gregory Price (Meta)" <gourry@gourry.net>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: "Gregory Price (Meta)" <gourry@gourry.net>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-trace-kernel@vger.kernel.org,
linux-rt-devel@lists.linux.dev, kernel-team@meta.com,
akpm@linux-foundation.org, mhocko@suse.com, rientjes@google.com,
shakeel.butt@linux.dev, rostedt@goodmis.org,
mhiramat@kernel.org, mathieu.desnoyers@efficios.com,
muchun.song@linux.dev, osalvador@suse.de, ljs@kernel.org,
liam@infradead.org, vbabka@kernel.org, rppt@kernel.org,
surenb@google.com, brendan.jackman@linux.dev,
hannes@cmpxchg.org, ziy@nvidia.com, bigeasy@linutronix.de,
clrkwllms@kernel.org, mgorman@techsingularity.net,
anshuman.khandual@arm.com, Bessel.Wang@huawei.com,
jiang.liu@huawei.com
Subject: Re: [PATCH v3 0/8] mm: fix allocator races with memory hotplug
Date: Wed, 28 Oct 2026 09:41:55 -0400 [thread overview]
Message-ID: <179319491540.2032926.7199366288730313291.b4-reply@b4> (raw)
In-Reply-To: <5e980194-d892-4b68-80fe-612c910c29d7@kernel.org>
On 2026-10-28 09:37 +0100, David Hildenbrand (Arm) wrote:
> On 10/21/26 04:39, Gregory Price (Meta) wrote:
> > Eight fixes for allocator paths that can act on state another CPU is
> > updating: zonelists rebuilt by memory hotplug, and the pagesets of a
> > zone that offlining empties.
> >
> > I've packaged these together because they're all related to hotplug.
> >
> > *** Backport note - Patches 5-7 build on patch 1: without it, their
> > retry is compiled out when CONFIG_MEMORY_HOTREMOVE=n.
> >
> > Most of these race conditions stem from zonelists being re-ordered
> > in-place at runtime during hotplug. The result is a mixture of failed
> > allocations, NULL dereferences, incorrect placement (GFP_KERNEL in
> > ZONE_MOVABLE), node misplacement, or incorrectly allowing hugetlb /
> > contig allocations on a node/zone otherwise not eligible.
> >
> > Most of these are incredibly narrow race conditions, but since the most
> > likely impacted machines are VMs with memory hotplug, the narrow
> > condition can more easily occur when a vCPU takes a long interrupt / VM
> > exit of some kind. I've made all of these race conditions
> > deterministics with a kprobe reproduction module described below.
>
> What's the status of this? "memory hotplug" caught my attention, but then then
> is all page_alloc material :)
>
I have a v4 with the requested tweaks and some performance analysis,
though i think there is some overlap with the other Fixes: series.
I can send it out and if it helps i can pull together a report on
overlap between the different Fixes: series.
~Gregory
--
~Gregory
prev parent reply other threads:[~2026-10-28 13:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-21 2:39 [PATCH v3 0/8] mm: fix allocator races with memory hotplug Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 1/8] mm/page_alloc: detect zonelist rebuilds from memory hot-add Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 2/8] mm/page_alloc: snapshot the preferred zone against shrink rebuilds Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 3/8] mm/mmzone: read each zoneref slot once when filtering by nodemask Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 4/8] mm/page_alloc: pass the zone, not the zoneref, to reclaim_retry_zone Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 5/8] mm/page_alloc: retry allocations that raced with a zonelist rebuild Gregory Price (Meta)
2026-10-22 2:41 ` sashiko-bot
2026-10-21 2:39 ` [PATCH v3 6/8] mm/hugetlb: retry the pool walk when the zonelist is rebuilt Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 7/8] mm/page_alloc: retry alloc_contig_pages() " Gregory Price (Meta)
2026-10-21 2:39 ` [PATCH v3 8/8] mm/page_alloc: keep a zone's pagesets when it goes empty Gregory Price (Meta)
2026-10-21 8:24 ` [PATCH v3 0/8] mm: fix allocator races with memory hotplug David Hildenbrand (Arm)
2026-10-21 13:24 ` Gregory Price (Meta)
2026-10-28 8:37 ` David Hildenbrand (Arm)
2026-10-28 13:41 ` Gregory Price (Meta) [this message]
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