Re:

[Greg Freemyer <greg.freemyer@gmail.com>]

On Sun, Apr 5, 2009 at 1:05 AM, Lelsie Rhorer <lrhorer@satx.rr.com> wrote:
>> Alternate theory - serious fsync performance issue
>>
>> I don't know if it's related, but there is a lot of recent discussion
>> related to fsync causing large delays in ext3.  Linus is saying his
>> highspeed SDD is seeing multisecond delays.  He is very frustrated
>> because the SDD should be more or less instantaneous.
>>
>> The current thread is http://markmail.org/message/adiyz3lri6tlueaf
>>
>> In one of the other threads I saw someone saying that in one test they
>> had a fsync() call take minutes to return.  Apparently no one yet
>> fully understands what is going on.  Seems like something that could
>> in some way be related to what you are seeing.
>
> Well, it could be.  I tried flushing the cashes numerous times while
> testing, but I never could see it made a difference one way or the other.
>

In a separate thread you said it was reiser and what I have seen
discussed is ext3, so you may be safe from that bug.

As to flushing caches, I don't think that is the same thing.    This
bug specifically impacts fsyncs on a small file while a heavy i/o load
is underway via other processes.  The elevators were being discussed
as part of the problem and fsync triggers different elevator logic
than sync or drop_caches does.

Greg
-- 
Greg Freemyer
Head of EDD Tape Extraction and Processing team
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
First 99 Days Litigation White Paper -
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html