Date: Fri, 14 Mar 2003 18:09:30 +0100 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: "Daniel C. Sobral" <dcs@tcoip.com.br> Cc: Garance A Drosihn <drosih@rpi.edu>, Juli Mallett <jmallett@FreeBSD.org>, Eivind Eklund <eivind@FreeBSD.org>, Mike Silbersack <silby@silby.com>, David Schultz <das@FreeBSD.org>, src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/vm ... SIGDANGER Message-ID: <7901.1047661770@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 14 Mar 2003 14:03:23 -0300." <3E720B5B.8090200@tcoip.com.br>
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In message <3E720B5B.8090200@tcoip.com.br>, "Daniel C. Sobral" writes: >There have been three suggestions to deal with low memory problem: > >* First, one way of telling the kernel that a certain process should be >excluded from the processes that can be killed under low memory conditions. > >* Second, SIGDANGER. malloc(3) keeps a (small) cache which can be flushed on SIGDANGER. >* Third, a sysctl to prevent overcommitting. With this on, memory would >be always immediatly allocated, instead of on-demand. With this, no >application would ever be killed. Either it aborted because it couldn't >allocate more memory, or it didn't. Since this can lock out users from a >machine, some of those that implemented this had a sort of reserve for >an interactive root process (which could still get exhausted, but whatever). * Fourth: A cheap syscall or sysctl which can be used to get a real-time qualified answer to the simple question: Is the system short of RAM ? Many programs (directly or implicitly through the use of malloc(3)) can adapt their behaviour, but lack the means to when to do that. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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