linux-kernel - RE: THP backed thread stacks

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Message-ID: <9725accc24aa4d76b01cdc9b210d12d4@AcuMS.aculab.com>
Date:   Sat, 18 Mar 2023 12:58:20 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Matthew Wilcox' <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: THP backed thread stacks

From: Matthew Wilcox
> Sent: 17 March 2023 17:53
...
> My understanding is that for a normal app (like, say, 'cat'), we'll
> allow up to an 8MB stack, but we only create a VMA that is 4kB in size
> and set the VM_GROWSDOWN flag on it (to allow it to magically grow).
> Therefore we won't create a 2MB page because the VMA is too small.

Is there anyway that glibc (or anything else) could request that
for a thread stack?

It would make the process 'memory size' reported by ps/top
much more meaningful for programs with threads.
I've noticed some (what should be) small programs having a
size (rss?) of 277m.
I'm sure a lot of it is thread stack.

	David

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