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Subject: [RFC] vsyscall_A0 LD_PRELOAD implementation
From: john stultz <johnstul@us.ibm.com>
To: Linus Torvalds <torvalds@transmeta.com>, andrea <andrea@suse.de>
Cc: Michael Hohnbaum <hbaum@us.ibm.com>,
       "Martin J. Bligh" <mbligh@aracnet.com>,
       george anzinger <george@mvista.com>,
       lkml <linux-kernel@vger.kernel.org>, ak@muc.de
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Here's an example use of the vsyscall via LD_PRELOAD.

Attached is an example library that can be LD_PRELOADED to alias glib's
gettimeofday function w/ the vsyscall implementation. I've also included
a quick performance test to give a rough idea of the savings this gives.

Example run on a SMP P4 box:

[jstultz@elm3b52 vsyscall_test]$ ./run.sh 
Normal gettimeofday
gettimeofday ( 1391621us / 1000000runs ) = 1.391620us
vsyscall LD_PRELOAD gettimeofday
gettimeofday ( 286567us / 1000000runs ) = 0.286567us

So it looks like a pretty big win.

thanks
-john


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