linux-kernel - Re: Task watchers v2

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Message-Id: <20061219042607.dcd865a3.pj@sgi.com>
Date:	Tue, 19 Dec 2006 04:26:07 -0800
From:	Paul Jackson <pj@....com>
To:	Matt Helsley <matthltc@...ibm.com>
Cc:	yanmin_zhang@...ux.intel.com, akpm@...l.org,
	linux-kernel@...r.kernel.org, jes@....com, hch@....de,
	viro@...iv.linux.org.uk, sgrubb@...hat.com, linux-audit@...hat.com,
	systemtap@...rces.redhat.com
Subject: Re: Task watchers v2

Matt wrote:
> Previous iterations of task watchers would prevent the code in these
> paths from being inlined. Furthermore, the code certainly wouldn't be
> placed near the table of function pointers (which was in an entirely
> different ELF section). By placing them adjacent to each other in the
> same ELF section we can improve the likelihood of cache hits in
> fork-heavy workloads (which were the ones that showed a performance
> decrease in the previous iteration of these patches).

Ah so - by marking some of the fork (and exit, exec, ...) routines
with the WATCH_TASK_* mechanism, you can compact them together in the
kernel's text pages, instead of having them scattered about based on
whatever source files they are in.

Nice.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.925.600.0401
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