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Re: [Qemu-devel] [PATCH 03/15] coroutine-ucontext: reduce stack size to

From: Dr. David Alan Gilbert
Subject: Re: [Qemu-devel] [PATCH 03/15] coroutine-ucontext: reduce stack size to 64kB
Date: Tue, 28 Jun 2016 11:57:07 +0100
User-agent: Mutt/1.6.1 (2016-04-27)

* Paolo Bonzini (address@hidden) wrote:
> On 28/06/2016 11:01, Peter Lieven wrote:
> > evaluation with the recently introduced maximum stack size monitoring 
> > revealed
> > that the actual used stack size was never above 4kB so allocating 1MB stack
> > for each coroutine is a lot of wasted memory. So reduce the stack size to
> > 64kB which should still give enough head room.
> If we make the stack this much smaller, there is a non-zero chance of
> smashing it.  You must add a guard page if you do this (actually more
> than one because QEMU will happily have stack frames as big as 16 KB).
> The stack counts for RSS but it's not actually allocated memory, so why
> does it matter?

I think I'd be interested in seeing the /proc/.../smaps before and after this
change to see if anything is visible and if we can see the difference
in rss etc.


> Paolo
Dr. David Alan Gilbert / address@hidden / Manchester, UK

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