Date: Tue, 19 Feb 2008 09:08:57 -0800 From: Jason Evans <jasone@freebsd.org> To: Igor Sysoev <is@rambler-co.ru> Cc: freebsd-current@FreeBSD.ORG Subject: Re: malloc(3) ignores RLIMIT_DATA Message-ID: <47BB0D29.5080403@freebsd.org> In-Reply-To: <20080219151809.GF57366@rambler-co.ru> References: <20080219151809.GF57366@rambler-co.ru>
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Igor Sysoev wrote:
> malloc(3) in FreeBSD 7 uses mmap() (then sbrk() on 32-bit platform)
> and ignores RLIMIT_DATA. FreeBSD 8's malloc() can be configured
> to use sbrk() only ("Dm"), but default setting is "DM".
I plan to merge these changes to RELENG_7 shortly after FreeBSD 7.0 is
released. As for the default, "DM", there is a strong argument that
malloc() should try hard to succeed, and only fail prematurely if the
user has added constraints via resource limits. Unfortunately,
RELENG_7_0 will not have the proper MALLOC_OPTIONS support to disable
mmap()-based allocation, but the release engineers prudently deemed the
necessary malloc(3) changes too risky so late in the release cycle.
> As sbrk() is less preferable because of framentation and race conditions,
> why not to create mmap() flag MMAP_DSS to check RLIMIT_DATA and to use it
> in malloc(3) ?
There has been general agreement among the people I've discussed this
issue with that the correct solution is to add a separate resource limit
for anonymously mapped memory, which would provide capabilities similar
to what your suggestion would provide.
Jason
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