[Lustre-devel] question about ldlm_server_glimpse_ast

[Cory Spitz <spitzcor@cray.com>]

Hello.

Increasing ldlm_timeout has no effect whatsoever if adaptive timeouts are
enabled.  See bug 22569.  I suggest that you tune up at_min instead.

Thanks,
-Cory


Oleg Drokin wrote:
> Hello!
> 
> On Apr 30, 2010, at 9:00 AM, John Hammond wrote:
>> I tested a patch which set rq_no_resend = 0 for glimpses, and found that 
>> clients only had about 6 seconds to reply before eviction.  Since 
>> eviction creates the possibility for data loss, a 6 second timeout was 
>> deemed too short for production.  (With the patch applied, it was easy 
>> for me to create cases where data was indeed lost.)  I was also able to 
> 
> Please note that the 6 second timeout is in fact common ldlm_timeout and it's
> not just glimpses that are bound by this value.
> any ldlm callbacks are required to reply withing this time, so if your
> network can have delays of more then this much, you need to consider
> increasing ldlm_timeout value (/proc/sys/lustre/ldlm_timeout).
> On the other hand if you have a packet loss issue, even if
> resending of glimpse ASTs would be present, we don't currently resend
> other ASTs so the situation still has a potential for evictions
> with subsequent possible data loss.
> 
> Bye,
>     Oleg
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