Re: BUG: Slowdown on 3000 socket-machines tracked down

Nick Piggin
2005-03-07T00:45:35Z

Christian Schmid wrote:

> Today I tested with 5000 sockets. The problem is the same like above but
> the more sockets there come, it just doesnt claim more bandwidth as it
> SHOULD of course do. It seems it doesn't slow down but it just doesnt
> scale anymore. The badwidth doesnt go over 80 MB/Sec, no matter what I
> do. Then I did the following: I raised lower_zone_protection to 1024
> (above I did 1024000 which is bullshit but it doesnt matter as it seems
> to just protect the whole low-mem which is what I want) and it was at 80
> MB. then I lowered to 0 again and suddenly it peaked up to full
> bandwidth (100 MB) for about 5 seconds until the whole protected area
> was in use. Then it slowed down drastically again.

This confirms my suspicion that lowmem / highmem scanning is not
properly balanced. When you raise lower_zone_protection a great
deal, lowmem is no longer used for pagecache, and your problem
goes away.

I gave you a patch to try for this - unfortunately I can't make
much more progress than that if I don't have a test case and you
can't test patches :\

Nick