BIND9 performance issues with SMP
JINMEI Tatuya /神明達哉
jinmei at isl.rdc.toshiba.co.jp
Tue Dec 21 22:24:08 PST 2004
>>>>> On Tue, 21 Dec 2004 17:17:32 -0700,
>>>>> Scott Long <scottl at freebsd.org> said:
>> 4. mutex contentions are VERY expensive (looks like much much more
>> expensive than other OSes), while trying to get a lock without a
>> contention is reasonably cheap. (Almost) whenever a user thread
>> blocks due to a lock contention, it is suspended with a system
>> call (kse_release), probably causing context switch. (I'm not
>> really sure if the system call overhead is the main reason of the
>> performance penalty though.)
> This might be related to what I said above. Where you observing this
> with process scope or system scope threads? Again, if scheduling
> decisions are not cheap in the UTS then there really is no point to
> SA/KSE.
I observed this with system scope threads. Note that "BIND+" I showed
in my previous message was modified so that it would specify
PTHREAD_SCOPE_SYSTEM. Yet this version ran slower as we increased
worker threads.
>> 6. at least so far, the ULE scheduler doesn't help improve the
>> performance (it even performs worse than the normal 4BSD
>> scheduler).
> With both types of threads?
Yes. Here are some results that were not contained in my previous
message:
#of process system
threads scope scope
1 3014 3090
2 3121 3179
3 2254 1922
4 1869 1405
(the tests were on FreeBSD 5.3 beta 7 w/ ULE + Xeon 700MHz x 4)
One remarkable difference is that ULE *relatively* improved the
results for process scope threads. However, the BIND server still
slowed down with multiple threads. That's why I said "ULE doesn't
help improve the performance".
> Have you tried Jeff's recent fixes to ULE?
I'm not sure. My experience with ULE was limited to the beta7 version
of FreeBSD 5.3, and I just gave up using it at that stage, having
seen everyone in this list said "ULE is broken, don't use it." If
beta7 did not contain the fixes you mentioned, I didn't try them.
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
jinmei at isl.rdc.toshiba.co.jp
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