Lustre discuss - Sep 2010 - Question about adaptive timeouts, not sending early reply

Hi all,

I''m trying to understand MDT logs and adaptive timeouts. After upgrade
to 1.8.4 and while users believed Lustre to be still in maintenance (no
activity), the MDT log just shows

Lustre: 19823:0:(service.c:808:ptlrpc_at_send_early_reply()) @@@
Couldn''t add any time (42/30), not sending early reply

Now, for historical reasons of running on a very shaky network, we load
the lustre module with

options ptlrpc at_max=6000
options ptlrpc at_history=6000
options ptlrpc at_early_margin=50

Right now however, the MDT reports:

lxmds:~# lctl get_param -n mdt.MDS.mds.timeouts
service : cur  30  worst  76 (at 1284734311, 0d19h33m39s ago)  30 30  30  30

Reading the manual on adaptive timeouts again, I conclude that if the
current estimate for timeout is 30 sec, the MDT is indeed hard pressed
to send an early reply 50 sec before that timeout occurs. The log
messages states something of the like, (42/30).
So, is my assessment correct? Are these log messages just due to the
stupid at_early_margin setting?

Regards,
Thomas

I believe this message says that the request timeout is on this 
transaction is 42s, but when Lustre
went to go ask for more time based on the current AT service estimate, 
it came up with 30s.
Since 30s is < 42s, it could not ask for more time.

Kevin


Thomas Roth wrote:
> Hi all,
>
> I''m trying to understand MDT logs and adaptive timeouts. After
upgrade
> to 1.8.4 and while users believed Lustre to be still in maintenance (>
no activity), the MDT log just shows
>
> Lustre: 19823:0:(service.c:808:ptlrpc_at_send_early_reply()) @@@
> Couldn''t add any time (42/30), not sending early reply
>
> Now, for historical reasons of running on a very shaky network, we load
> the lustre module with
>
> options ptlrpc at_max=6000
> options ptlrpc at_history=6000
> options ptlrpc at_early_margin=50
>
> Right now however, the MDT reports:
>
> lxmds:~# lctl get_param -n mdt.MDS.mds.timeouts
> service : cur  30  worst  76 (at 1284734311, 0d19h33m39s ago)  30 30  30 
30
>
> Reading the manual on adaptive timeouts again, I conclude that if the
> current estimate for timeout is 30 sec, the MDT is indeed hard pressed
> to send an early reply 50 sec before that timeout occurs. The log
> messages states something of the like, (42/30).
> So, is my assessment correct? Are these log messages just due to the
> stupid at_early_margin setting?
>
> Regards,
> Thomas
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