From: Jeff King <peff@peff.net>
Date: Fri, 24 Oct 2008 18:20:31 GMT
Subject: Re: git performance
Message-ID: <20081024182031.GA11287@coredump.intra.peff.net>
In-Reply-To: <alpine.LFD.2.00.0810241050310.3287@nehalem.linux-foundation.org>

On Fri, Oct 24, 2008 at 10:53:20AM -0700, Linus Torvalds wrote:

> >   echo 1 >/proc/sys/vm/drop_caches
> 
> Use "echo 3" instead of "1".
> 
> It's actually a bitmask, with bit 0 being "data" (pagecache) and bit 1 
> being "metadata" (inodes and directory caches).
> 
> And since git (or any SCM) is very metadata-intensive, you really should 
> make sure to drop metadata too, otherwise your caches won't be really very 
> cold at all.
> 
> (But it obviously depends on the operation you're testing - some are more 
> about the inodes and directories, others are about file data access).

Ah, thanks. In this case, he was interested in walking the directory
tree, so the metadata caching was indeed very important.

-Peff