Re: 2.4.8-pre1 and dbench -20% throughput

[Steven Cole <elenstev@mesatop.com>]

On Friday 27 July 2001 16:34, Daniel Phillips wrote:
> On Friday 27 July 2001 23:08, Roger Larsson wrote:
> > Hi all,
> >
> > I have done some throughput testing again.
> > Streaming write, copy, read, diff are almost identical to earlier 2.4
> > kernels. (Note: 2.4.0 was clearly better when reading from two files
> > - i.e. diff - 15.4 MB/s v. around 11 MB/s with later kenels - can be
> > a result of disk layout too...)
> >
> > But "dbench 32" (on my 256 MB box) results has are the most
> > interesting:
> >
> > 2.4.0 gave 33 MB/s
> > 2.4.8-pre1 gives 26.1 MB/s (-21%)
> >
> > Do we now throw away pages that would be reused?
> >
> > [I have also verified that mmap002 still works as expected]
>
> Could you run that test again with /usr/bin/time (the GNU time
> function) so we can see what kind of swapping it's doing?
>

I also saw a significant drop in dbench 32 results.
Here are a few more data points, this time comparing 2.4.8-pre1 with 2.4.7.

2.4.7   9.3422 MB/sec vs 2.4.8-pre1   6.88884 MB/sec average of 3 runs

The system under test has 384 MB of memory, and did not go
into swap during the test.  I performed a set of three runs immediately after
a boot, and with no pauses in between individual runs.  I used time ./dbench 32
and caputured the output in a file using script `uname -r`.  The tests were done
with X and KDE running, but no other activity.

Here are the results of the six runs:

Steven
-----------------------------------------------------------------------------
2.4.7       average 9.3422 MB/sec

Throughput 9.2929 MB/sec (NB=11.6161 MB/sec  92.929 MBit/sec)
34.11user 238.89system 7:34.59elapsed 60%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1008major+1402minor)pagefaults 0swaps

Throughput 9.56338 MB/sec (NB=11.9542 MB/sec  95.6338 MBit/sec)
34.07user 262.44system 7:22.72elapsed 66%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1008major+1402minor)pagefaults 0swaps

Throughput 9.17032 MB/sec (NB=11.4629 MB/sec  91.7032 MBit/sec)
33.79user 248.46system 7:41.62elapsed 61%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1008major+1402minor)pagefaults 0swaps

-----------------------------------------------------------------------------
2.4.8-pre1  average 6.88884 MB/sec

Throughput 6.8078 MB/sec (NB=8.50975 MB/sec  68.078 MBit/sec)
34.30user 358.35system 10:21.57elapsed 63%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1008major+1402minor)pagefaults 0swaps

Throughput 6.91993 MB/sec (NB=8.64992 MB/sec  69.1993 MBit/sec)
33.62user 369.55system 10:11.43elapsed 65%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1008major+1402minor)pagefaults 0swaps

Throughput 6.93879 MB/sec (NB=8.67349 MB/sec  69.3879 MBit/sec)
33.33user 341.58system 10:09.77elapsed 61%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1008major+1402minor)pagefaults 0swaps