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

Christian Schmid
2005-03-14T04:54:07Z

>>This effect appeared on 1 task and on 200 tasks. I dont know what it is, but with HT off it doesnt
>>appear anymore. The slow-down still appears when lower_zone_protection is set to 0 but the peak at
>>80 MB disappeared when set to 1024. I am now running at 95 MB/Sec smoothly.
>>
>
> OK well that is a good result for you. Thanks for sticking with it.
> Unfortunately you'll probably not want to test any patches on your
> production system, so the cause of the problem will be difficult to
> fix.
>
> I am working on patches which improve HT performance in some
> situations though, so with luck they will cure your problems too.
> Basically I think SMP "balancing" is too aggressive - and this may
> explain why 2.6.10 was worse for you, it had patches to *increase*
> the aggressiveness of balancing.
>
> The other thing that worries me is your need for lower_zone_protection.
> I think this may be due to unbalanced highmem vs lowmem reclaim. It
> would be interesting to know if those patches I sent you improve this.
> They certainly improve reclaim balancing for me... but again I guess
> you'll be reluctant to do much experimentation :\

I have tested your patch and unfortunately on 2.6.11 it didnt change anything :( I reported this
before, or do you mean something else? I am of course willing to test patches as I do not want to
stick with 2.6.10 forever.