Re: BUFCACHEPERCENT.

[Chris Cameron <chris_(_at_)_upnix_(_dot_)_com>]

A simple 'grep -ri "Some text here" .' in my couple hundred meg Maildir 
folder will always take longer the first time than the second time; 
when searching for different text too.

$ time grep -ri "dirty shirt" .
    6.54s real     0.86s user     1.35s system
$ time grep -ri "hairy back" .
    1.96s real     1.21s user     0.24s system
$


Before I raised BUFCACHEPERCENT, I'm certain this wasn't the case as I 
often find myself on the phone (in a hurry) trying to find past emails.

I've also just tried this on other OBSD machines I have lying around, 
with an unchanged cache and grep's in a row don't seem to speed up 
unless the folder is quite small.

This is on 3.4 with mirrored SCSI drives.


Chris


On June 9, 2004 12:36 pm, you wrote:
> On Wed, 9 Jun 2004, Chris Cameron wrote:
> > I know touching the kernel is taboo, but quite recently I've raised
> > my BUFCACHEPERCENT to 25 and have noticed improvements in repeated
> > grep's.
>
> this is a near impossibility if you're using grep from 3.4 or 3.5, as
> it should be using mmap and therefore not touching the buffer cache
> at all.
>
> more details would be interesting.