Date: Tue, 25 Mar 2003 14:21:40 -0300 From: "Daniel C. Sobral" <dcs@tcoip.com.br> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: David Schultz <das@FreeBSD.ORG>, 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: <3E809024.1050303@tcoip.com.br> In-Reply-To: <14382.1048580753@critter.freebsd.dk> References: <14382.1048580753@critter.freebsd.dk>
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Poul-Henning Kamp wrote:
> If we are going to do this, we should do it right.
>
> Doing it right means that we should also be sharing enough information
> with userland, so that userland can adapt.
>
> Take a simple example: It makes sense for a program like fsck to
> use all the RAM it can get hold off as cache, but it does not make
> sense for the cache to be paged out.
>
> As I see it, there is a need for several mechanisms:
SIGDANGER actually takes care of two of these steps:
>
> 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.
SIGDANGER is sent to processes at threshold #1, alerting them the
situation has become serious.
> 3. A mechanism to influence the "Who do we kill ?" decision once
> things have gone from bad to worse.
When the situation becomes so critical that the system cannot proceed
without first killing something, it will only kill a process which has
registered SIGDANGER if there are no other suitable process.
--
Daniel C. Sobral (8-DCS)
Gerencia de Operacoes
Divisao de Comunicacao de Dados
Coordenacao de Seguranca
TCO
Fones: 55-61-313-7654/Cel: 55-61-9618-0904
E-mail: Daniel.Capo@tco.net.br
Daniel.Sobral@tcoip.com.br
dcs@tcoip.com.br
Outros:
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-- Snoopy
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