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Date: Wed, 10 Apr 2024 17:23:18 -0400
From: Peter Xu <peterx@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Lokesh Gidra <lokeshgidra@google.com>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>,
	Alistair Popple <apopple@nvidia.com>
Subject: Re: [PATCH] mm: Always sanity check anon_vma first for per-vma locks
Message-ID: <ZhcDRmyYkMGPgs4F@x1n>
References: <20240410170621.2011171-1-peterx@redhat.com>
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 <ZhcAVYVFSdX5Binc@casper.infradead.org>
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On Wed, Apr 10, 2024 at 10:10:45PM +0100, Matthew Wilcox wrote:
> > I can do some tests later today or tomorrow. Any suggestion you have on
> > amplifying such effect that you have concern with?
> 
> 8 socket NUMA system, 800MB text segment, 10,000 threads.  No, I'm not
> joking, that's a real customer workload.

Well, I believe you, but even with this, that's a total of 800MB memory on
a giant moster system... probably just to fault in once.

And even before we talk about that into details.. we're talking about such
giant program running acorss hundreds of cores with hundreds of MB text,
then... hasn't the program developer already considered mlockall() at the
entry of the program?  Wouldn't that greatly beneficial already with
whatever granule of locks that a future fault would take?

-- 
Peter Xu