Odd performance problem (hitching)

Don Lewis truckman at FreeBSD.org
Mon Aug 29 18:15:48 GMT 2005


On 25 Aug, Alexander Kabaev wrote:
> On Fri, 26 Aug 2005 09:13:53 +0930
> "Daniel O'Connor" <doconnor at gsoft.com.au> wrote:
> 
>> I updated to -current recently (from an earlier -current) and haven't
>> changed any kernel options, but now the systems seems to 'hitch'
>> fairly frequently. ie the system will run fine then stall for half a
>> second or so, then continue as normal. It is most noticeable when
>> playing music.
>> 
>> If I turn powerd off and run the CPU at full speed it works better,
>> but it still happens on occasion so I am guessing powerd isn't the
>> problem per se, but just makes it worse.
>> 
>> I am not 100% sure when the problem started but if I get time I will
>> try a binary search to find out.. It believe around 6.0-BETA1 (30
>> July) was OK, but I don't have any more data points yet.
>> 
>> I've attached my dmesg and kernel config file if it helps.
>> 
>> -- 
>> Daniel O'Connor software and network engineer
>> for Genesis Software - http://www.gsoft.com.au
>> "The nice thing about standards is that there
>> are so many of them to choose from."
>>   -- Andrew Tanenbaum
>> GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
> 
> 
> Can you try backing out this commit?
> 
> http://cvsweb.FreeBSD.org/src/sys/kern/vfs_subr.c.diff?r1=1.641&r2=1.642

Any more info on this problem?  I just got my MFC reminder for this
change and I don't want to request permission for the MFC until I know
for sure that it (or 1.636, which is also has a pending MFC) isn't the
cause of the problem.

What else is happening on machine when the symptoms occur?  I would only
expect vfs_subr.c 1.636 and 1.642 to affect the behaviour if there was a
lot of file system activity that put pressure on the system to free up
vnodes.




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