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Re: [PATCH] linux-user: Reserve space for brk

From: Alex Bennée
Subject: Re: [PATCH] linux-user: Reserve space for brk
Date: Mon, 20 Jan 2020 13:46:07 +0000
User-agent: mu4e 1.3.6; emacs 28.0.50

Warner Losh <address@hidden> writes:

> On Fri, Jan 17, 2020 at 4:03 PM Richard Henderson <
> address@hidden> wrote:
>> With bad luck, we can wind up with no space at all for brk,
>> which will generally cause the guest malloc to fail.
> ...
>> The choice of 16MB is somewhat arbitrary.  It's enough for libc
>> to get going, but without being so large that 32-bit guests or
>> 32-bit hosts are in danger of running out of virtual address space.
>> It is expected that libc will be able to fall back to mmap arenas
>> after the limited brk space is exhausted.
> The biggest abuser of brk() is emacs, so according to one old wag
> this should be 80MB. Eighty Megabytes And Continuously Swapping.

Is this related to the dumper that it uses? I guess the new dumper
system isn't a problem as I was able to run emacs -nw -q on the buster
image without problem.

Alex Bennée

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