[Lustre-discuss] understanding max_rpc_in_flight

[teng wang]

Hi Andreas and Artem,


Thanks for your answer. If so, does the server have to reply to

every RPC request after the RDMA transfer for each RPC? Or only

reply once for transferring all 'max_rpc_in_flight' RPCs?


What's the benefit of keeping 'max_rpc_in_flight'? Given that each

RDMA handles only data transfer for 1 RPC each time,

even it allows 'max_rpc_in_flight', it still has to transfer the data for

'max_rpc_in_flight'  times instead of once for all. So it seems the

only benefit may come from the overlapping between transferring

RPC requests instead of transferring the data.


Is RPC transfer handled by the service threads, which also perform I/O?

Or the I/O functionality and RPC are handled by separate threads?


Thanks,

Teng

On Thu, Mar 12, 2015 at 2:54 AM, Artem Blagodarenko <
artem.blagodarenko at seagate.com> wrote:

> Hello Teng,
>
> Probably the patch that adds 4 mb rpc support is what you need. There is
> quite detailed explanation in patch's description.
>
>
> http://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commit;h=cf6c739fa3934aebd0893165d69e254a76c6d51e
>
> Best regards,
> Artem Blagodarenko
>
> On Thu, Mar 12, 2015 at 3:15 AM, teng wang <tzw0019 at gmail.com> wrote:
>
>> Dear All,
>>
>> Is there any concrete explanation of max_rpc_in_flight?
>> Most definitions online simply interpret it as the name suggests.
>> Can any one explain it from the I/O path?
>> For example, when the client wants to write, it sends an RPC
>> for the write to the object server. The server then pulls
>> the data with RDMA and commit to disks. During this process,
>> only 1 RPC is issued. What's the situation for 'max_rpc_in_flight'?
>> Could any one explain it more concretely?
>>
>> Thanks,
>> Teng
>>
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>>
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>>
>>
>
>
> --
> Artem Blagodarenko Ph.D.*·* SW Developer on my.seagate.com
> Seagate Technology, LLC
> www.seagate.com
>
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