From: Andrew Morton <[email protected]>
> Paolo Ciarrocchi wrote:
> >
> > Hi Andrew/Rik/Con/all
> >
> > Andrew, I promised you to run a few tests
> > using osdb (http://www.osdb.org with 40M of data)against both
> > 2.4.19 and 2.5.52 booting the kernel with the
> > mem=XXM paramter.
> >
> > I also played with the /proc/sys/vm/swappiness
> > parameter, I've ran all the tests with the standard
> > swappiness value (60), with 80 and 100.
> >
> > 100 means the 2.4 behaviour, isn't it ?
>
> Not really. swappiness=100 is strict LRU, treating pagecache and
> mapped-into-process-memory pages identically. Smaller values will
> make the kernel prefer to preserve mapped-into-process-memory.
>
> > Looking at the results it seems that the "standard"
> > value is too low, probably 80 is the best one.
> > What do you think ?
>
> I would agree with that.
>
> > ...
> >
> > 2.4.19 all x 778.65 seconds (0:12:58.65)
> > 2.5.52 all 60 768.98 seconds (0:12:48.98)
> > 2.5.52 all 80 770.43 seconds (0:12:50.43)
> > 2.5.52 all 100 771.76 seconds (0:12:51.76)
>
> Only 1% difference. On my 4xPIII with mem=128M, 2.4.20-pre2 took
> 1080.55 seconds and 2.5.52-mm3 took 991.03. That's 9% faster, and
> from the profile:
>
> c010a858 system_call 192 4.3636
> c011e518 current_kernel_time 201 3.3500
> c012cdbc __generic_file_aio_read 214 0.4652
> c012bba0 kallsyms_lookup 219 0.8295
> c012ccec file_read_actor 230 1.1058
> c0145abc fget 318 4.1842
> c01d3ed4 radix_tree_lookup 384 3.8400
> c0144be0 vfs_read 409 1.3279
> c01315f4 check_poison_obj 695 7.8977
> c012c964 do_generic_mapping_read 1007 1.1988
> c01d7ae0 __copy_user_intel 34130 213.3125
> c0108a58 poll_idle 299231 3562.2738
>
> it appears that this benefit came from the special usercopy code.
> What sort of CPU are you using?
It is a PIII@800.
Ciao,
Paolo
--
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