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From Aaron Bannert <aa...@clove.org>
Subject Re: performance: using mlock(2) on httpd parent process
Date Wed, 20 Mar 2002 18:25:11 GMT
On Thu, Mar 21, 2002 at 02:14:04AM +0800, Stas Bekman wrote:
> But if the system needs to page things out, most of the parent process's 
>  pages will be scheduled to go first, no? So we are talking about a 
> constant page-in/page-out from/to the parent process as a performance 
> degradation rather than memory unsharing. Am I correct?
[...]
> Well, the system coming close to zero of real memory available. The 
> parent process starts swapping like crazy because most of its pages are 
> LRU, slowing the whole system down and if the load doesn't go away, the 
> system takes a whirl down to a halt.

FWIW, Solaris 8 introduced "priority paging", which basicly means
that pages that are non-executable will be swapped out earlier than
higher-priority executable pages. This of course introduces nasty little
tricks like marking a data file as executable just to ensure that it
gets priority paging.

I'm not sure how this affects mod_perl and it's "data is runtime-compiled
bytecode" situation, but it means that we get it for free w/ httpd and
all its dependent libraries (and DSOs).

-aaron

p.s. It can be enabled on Solaris 7, it's just not on by default.


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