Date: Tue, 25 Mar 2003 02:44:54 -0800 From: David Schultz <das@FreeBSD.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Garance A Drosihn <drosih@rpi.edu>, Dan Nelson <dnelson@allantgroup.com>, Wes Peters <wes@softweyr.com>, freebsd-arch@FreeBSD.org Subject: Re: Patch to protect process from pageout killing Message-ID: <20030325104454.GA5934@HAL9000.homeunix.com> In-Reply-To: <14382.1048580753@critter.freebsd.dk> References: <20030325075342.GA5450@HAL9000.homeunix.com> <14382.1048580753@critter.freebsd.dk>
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Thus spake Poul-Henning Kamp <phk@phk.freebsd.dk>: > As I see it, there is a need for several mechanisms: > > 1. A mechanism to export to userland enough information about the > current RAM availability, so that phkmalloc and application > specific code can make intelligent choices before things go bad. > > 2. A mechanism to alert userland to the fact that things _have_ gone > bad. > > 3. A mechanism to influence the "Who do we kill ?" decision once > things have gone from bad to worse. I completely agree, and in my last email I attempted to address the fact that #2 and #3 are distinct, and to say that people shouldn't be complaining about Wes's solution to #3 because it doesn't address #2. For #1 and #2, we could have a SIGVM (your terminology from the *last* time this came up) to notify processes about material changes in global resource availability. Applications could then look at that "kernel info" page upon receiving the signal and take appropriate action. I think the hardest part is getting applications to use a proprietary facility. (For example, look at how few people are using kqueue for all of its advantages.) Certainly it could be added to base system programs, but it would be most useful for applications such as postgresql and apache. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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