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Re: [Gnu-arch-users] Re: [PATCH] arch speedups on big trees

From: Dustin Sallings
Subject: Re: [Gnu-arch-users] Re: [PATCH] arch speedups on big trees
Date: Mon, 12 Jan 2004 09:48:18 -0800

On Jan 12, 2004, at 6:25, David Allouche wrote:

What this does is just mallocing and touching memory until the kernel
out-of-memory killer nukes the program.

That flushes all kernel caches and buffers as well as possible. Only
problem is _if_ you have an oversized swap, it will be slow. Anyway
having an oversized swap is a bad thing, because real-life programs
sometimes go berserk this way, and with too big a swap they can make
your system unusable for ages before the OOM killer comes.

I wrote a similar one to figure to clean out the caches (which greatly helped with performance in a few cases), and try to figure out how large of a block can be allocated on a system. It does this by grabbing larger blocks until ENOMEM, and then shrinking it by one until I don't get an ENOMEM.

The problem I had the last time I ran it wasn't an oversized swap, but a dynamic swap (swap was dynamically growing with demands). That was a bit unfortunate.

Dustin Sallings

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