On Wed, 2017-08-23 at 17:05 -0400, Chuck Lever wrote:
> Adopt the use of xprt_pin_rqst to eliminate contention between
> Call-side users of rb_lock and the use of rb_lock in
> rpcrdma_reply_handler.
>
> This replaces the mechanism introduced in 431af645cf66 ("xprtrdma:
> Fix client lock-up after application signal fires").
>
> Use recv_lock to quickly find the completing rqst, pin it, then
> drop the lock. At that point invalidation and pull-up of the Reply
> XDR can be done. Both are often expensive operations.
>
> Finally, take recv_lock again to signal completion to the RPC
> layer. It also protects adjustment of "cwnd".
>
> This greatly reduces the amount of time a lock is held by the
> reply handler. Comparing lock_stat results shows a marked decrease
> in contention on rb_lock and recv_lock.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> Hi-
>
> If Trond's lock contention series is going into v4.14, I'd like you
> to consider this one (applied at the end of that series) as well.
> Without it, NFS/RDMA performance regresses a bit after the
> first xprt_pin_rqst patch is applied. Thanks!
>
If Anna is OK with it, then I can apply this patch once she's sent me
the pull request for the other RDMA client patches.
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
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