[Lustre-discuss] RPC packing

[Drokin, Oleg]

btw, it should be noted that by the same file we really mean "same object".
IF you have a file that's striped two-way with stripe size of 1M,
then two 4k writes, one at offset 0 and another at offset 1M would not
be merged into single rpc because they would be sent to different servers,
but two writes at offsets 0 and 512K would be merged into same RPC.

On Oct 7, 2014, at 8:33 PM, Drokin, Oleg wrote:

> Hello!
> 
> On Oct 7, 2014, at 11:03 AM, teng wang wrote:
>> I know the RPC will pack the
>> client's data into 4MB buffer and transfer. The question is does the
>> client pack the writes even the writes on the client belong
>> to noncontiguous extents of the same file? Say, 1 client is issuing
>> two writes on two noncontiguous extents of the same file, the first write
>> from offset 0 to 16KB-1, the second write from 32KB to 
>> 48KB-1,  apparently these two writes are noncontiguous, so
>> will the two writes still be packed into the 4MB buffer?
> 
> Yes, noncontiguous writes of the same type (i.e. you cannot mix diret io
> and normal directio) would be packed in the same RPC
> 
> Bye,
>    Oleg
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