Re: endless sync on bdi_sched_wait()?

From: Jeff Moyer
Date: Thu Apr 01 2010 - 16:15:22 EST

Dave Chinner <david@xxxxxxxxxxxxx> writes:

> On Thu, Apr 01, 2010 at 01:42:42PM +0300, Denys Fedorysychenko wrote:
>> Thats correct, it is quite busy cache server.
>> Well, if i stop squid(cache) sync will finish enough fast.
>> If i don't - it took more than hour. Actually i left that PC after 1 hour, and
>> it didn't finish yet. I don't think it is normal.
>> Probably sync taking new data and trying to flush it too, and till he finish
>> that, more data comes.
>> Actually all what i need - to sync config directory. I cannot use fsync,
>> because it is multiple files opened before by other processes, and sync is
>> doing trick like this. I got dead process, and only fast way to recover system
>> - kill the cache process, so I/O pumping will stop for a while, and sync()
>> will have chance to finish.
>> Sure there is way just to "remount" config partition to ro, but i guess just
>> sync must flush only current buffer cache pages.
>> I will do more tests now and will give exact numbers, how much time it needs
>> with running squid and if i kill it shortly after running sync.
> Ok. What would be interesting is regular output from /proc/meminfo
> to see how the dirty memory is changing over the time the sync is
> running....

This sounds familiar:

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