Re: File System Performance

Andrew Morton
2001-11-12T21:45:23Z

Steve Lord wrote:
>
> ...
>
> I tried an experiment which puzzled me somwhat:
>
> > mount /xfs
> > cd /xfs/lord/xfs-linux
> > time tar cf /dev/null linux
>
> real 0m7.743s
> user 0m0.510s
> sys 0m1.380s
>
> > hdparm -t /dev/sda5
>
> /dev/sda5:
> Timing buffered disk reads: 64 MB in 3.76 seconds = 17.02 MB/sec
>
> > du -sk linux
> 173028 linux
>
> The tar got ~21 Mbytes/sec.
>

It's tar. It cheats. It somehow detects that the
output is /dev/null, and so it doesn't read the input files.
I think.

akpm-1:/opt> l
total 562884
-rw-r--r-- 1 akpm akpm 575785370 Apr 8 2001 backup

akpm-1:/opt> time tar cf /dev/null backup
tar cf /dev/null backup 0.02s user 0.00s system 4% cpu 0.422 total

That's 570 megs in 0.4 seconds. Impressive.

So I just use
time (find dir -type f | xargs cat > /dev/null)

> In our cvs tree cmd/xfsprogs/tests/src/fsstress.c

OK, thanks.

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