Re: 2.5.65-mm1

William Lee Irwin III
2003-03-18T21:29:37Z

On Tue, Mar 18, 2003 at 03:11:04AM -0800, Andrew Morton wrote:
> . An updated version of Russell's PCMCIA patches
> . Lots more anticipatory scheduler work.
> . It turns out that calling disk request_fns from timer/tasklet context is
> not permitted because a few old drivers like to sleep in that function.
> keventd cannot be used for this because it can deadlock. So another
> kernel thread per CPU has been reluctantly added.

So far so good. There are couple of non-critical things I noticed.
On my home machine, 600MHz Athlon w/768MB RAM, Adaptec 39160 + U160 disk

pte_chain: 4644KB 4661KB 99.64
dentry_cache: 987KB 1275KB 77.47
radix_tree_node: 988KB 1233KB 80.14
reiser_inode_cache: 755KB 1181KB 63.93
biovec-BIO_MAX_PAGES: 768KB 780KB 98.46
size-4096: 624KB 624KB 100.0
inode_cache: 457KB 457KB 100.0
pgd: 432KB 432KB 100.0

shpte really blew the doors off of pte_chains for my home box and
slightly more than halved pagetable space. It really helps keep things
from swapping, a good 4-6 MB of pte_chain + pagetable space. I wish for
it back relatively often.

OTOH objrmap appears to have blown page_*_rmap() functions off the
profiles on the execution time front.

Window wiggle test times (ms):

inter-arrival service response
------------- ------- --------
113.828 0.093 4.702
113.828 0.093 4.702
113.828 0.093 4.702
113.828 0.093 4.702
113.828 0.093 4.702
56.762 0.090 4.593
56.762 0.090 4.593
56.762 0.090 4.593
56.762 0.090 4.593
56.762 0.090 4.593
106.250 0.088 4.545
51.944 0.135 6.133
34.006 0.172 7.345
27.087 0.194 7.276
26.807 0.120 6.549
27.975 0.128 6.721
31.292 0.161 7.278
32.952 0.147 6.692
32.952 0.147 6.692
32.952 0.147 6.692
32.952 0.147 6.692
32.952 0.147 6.692

This is really the only visible task scheduling pathology. The user
observable effect is that now transparent xterms "flash" when being
wiggled, where before they merely showed some refresh jitter. But it's
a vast net improvement; good work on mingo's part.

I've not been noticing the more refined aspects of io scheduling.
Basically once deadline-iosched hit, my home machine was very happy,
and the gains after mostly slight. There's some of app startup time
that appears to have been trimmed down that may have come from this.
I noticed it while booting but by and large I don't spawn new large
tasks regularly, so it sort of doesn't do as much for me as others.
It could also be due to the prefaulting or a combined effect.

-- wli