Re: [PATCH v2 06/10] xprtrdma: Enable pad optimization

Chuck Lever
2014-11-10T14:54:36Z

On Nov 10, 2014, at 8:36 AM, Anna Schumaker <Anna.Schumaker@netapp.com> wrote:

> Hey Chuck,
>
>
> On 11/08/2014 08:14 PM, Chuck Lever wrote:
>> The Linux NFS/RDMA server used to reject NFSv3 WRITE requests when
>> pad optimization was enabled. That bug was fixed by commit
>> e560e3b510d2 ("svcrdma: Add zero padding if the client doesn't send
>> it").
>
> Do we need to worry about backwards compatibility with servers that don't have this patch?

My impression is that we have a window where the server is assumed not
to work and thus is not enabled in distributions, and that therefore
changes like this are allowed. I could be wrong. Bruce, any guidance
on this?

In any event, if things break, they break immediately, and the fix is
simply to set this feature flag via /proc.

> Anna
>
>>
>> We can now enable pad optimization on the client, which helps
>> performance and is supported now by both Linux and Solaris servers.
>>
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
>> net/sunrpc/xprtrdma/transport.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
>> index cfe9a81..8ed2576 100644
>> --- a/net/sunrpc/xprtrdma/transport.c
>> +++ b/net/sunrpc/xprtrdma/transport.c
>> @@ -73,7 +73,7 @@ static unsigned int xprt_rdma_max_inline_read = RPCRDMA_DEF_INLINE;
>> static unsigned int xprt_rdma_max_inline_write = RPCRDMA_DEF_INLINE;
>> static unsigned int xprt_rdma_inline_write_padding;
>> static unsigned int xprt_rdma_memreg_strategy = RPCRDMA_FRMR;
>> - int xprt_rdma_pad_optimize = 0;
>> + int xprt_rdma_pad_optimize = 1;
>>
>> #ifdef RPC_DEBUG
>>
>>
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com