[Gluster-devel] [puzzle] readv operation allocate iobuf twice

[Raghavendra Gowdappa]

----- Original Message -----
> From: "Zhengping Zhou" <johnzzpcrystal at gmail.com>
> To: gluster-devel at gluster.org
> Sent: Tuesday, July 12, 2016 9:28:01 AM
> Subject: [Gluster-devel] [puzzle] readv operation allocate iobuf twice
> 
> Hi all:
> 
>     It is a puzzle to me that we  allocate rsp buffers for rspond
> content in function client3_3_readv, but these rsp parameters hasn't
> ever been saved to struct saved_frame in submit procedure. 

Good catch :). We were aware of this issue, but the fix wasn't prioritized. Can you please file a bug on this? If you want to send a fix (which essentially stores the rsp payload ptr in saved-frame and passes it down during rpc_clnt_fill_request_info - as part of handling RPC_TRANSPORT_MAP_XID_REQUEST event in rpc-clnt), please post a patch to gerrit and I'll accept it. If you don't have bandwidth, one of us can send out a fix too.

Again, thanks for the effort :).

regards,
Raghavendra

> Which means
> the iobuf will reallocated by transport layer in function
> __socket_read_accepted_successful_reply.
>     According to  the commnet of fucntion rpc_clnt_submit :
>     1. Both @rsp_hdr and @rsp_payload are optional.
>     2. The user of rpc_clnt_submit, if wants response hdr and payload in its
>     own
>         buffers, then it has to populate @rsphdr and @rsp_payload.
>         ....
>     The rsp_payload  is optional, ransport layer will not reallocate
> rsp buffers if
> it populated. But the fact is readv operation will allocate rsp buffer twice.
> 
> Thanks
> Zhengping
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