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

Christian Schmid
2005-05-28T03:19:06Z

Hi.

I want to give the newest report for the vm-lock problem. It seems the problem is getting less
critical in every new release. I am currently using 2.6.12-rc5. The problem with the massive vm-lock
appears as always when 3500 sockets are reached as reported in earlier mails. The problem suddenly
disappears when I set lowmem_reserve_ratio to "1 1" AND min_free_kbytes to 1024000. It only starts
to appear again when reaching around 7000 sockets. -rc3 for example slowed down at 4500 sockets again.

I am very sure its a vm-lock because for example reading /proc/sys/vm/lowmem_reserve_ratio needs no
time with < 3500 sockets. While testing with 7000 sockets, I had to wait 20-30 seconds until the
"file" was opened.

Any suggestions? Dual Xeon 3,6 GHz with 8 GB Ram.

Nick Piggin wrote:
> On Mon, 2005-03-14 at 05:53 +0100, Christian Schmid wrote:
>
>
>>>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.
>
>
> Well I hope that scheduler developments in progress will put future
> kernels at least on par with 2.6.10 again (and hopefully better).
>
> Yes you did report that my patch didn't help 2.6.11, but could those
> results have been influenced by the suboptimal HT scheduling? If so,
> I was interested in the results with HT turned off.
>
> Nick
>
>
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