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Date: Fri, 22 Mar 2002 03:08:58 -0600 (CST)
From: Mike Silbersack <silby@silby.com>
To: David Malone <dwmalone@maths.tcd.ie>
Cc: cvs-committers@FreeBSD.org, <cvs-all@FreeBSD.org>
Subject: Re: cvs commit: src/sys/ufs/ufs ufs_dirhash.c 
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On Wed, 20 Mar 2002, David Malone wrote:

> > >                                mean #probes for
> > >                     home dir  mh inbox  news/cancel  tmp    squid2  squid3
> > >   old   successful  1.02      3.19      4.07         1.10    7.85   2.06
> > >   new   successful  1.04      1.32      1.27         1.04    1.93   1.17
> > >
> > >   old unsuccessful  1.08      4.50      5.37         1.17   10.76   2.69
> > >   new unsuccessful  1.08      1.73      1.64         1.17    2.89   1.37
>
> > What do the numbers look like w/o DIRHASH?  I'm curious...
>
> The closest thing I could produce to a direct comparison would be
> the number of blocks fetched from the buffer cache. For a successful
> lookup this is (dirsize/2) and for an unsuccessful lookup (dirsize).
> For the table above:
>
>                         home dir  mh inbox  news/cancel  tmp    squid2  squid3
> unsuccessful            47        58        3987         24     8       13
>   successful            23.5      29        1993.5       12     4        6.5

Hmph.  Here I thought you were increasing performance enormously, and it
turns out that the "old" DIRHASH is still far better than the baseline.
Oh well... :)

Mike "Silby" Silbersack


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