On Mon, 2 May 2011 21:40:08 -0400
andros@xxxxxxxxxx wrote:
> From: Andy Adamson <andros@xxxxxxxxxx>
>
> Hookup TCP congestion feedback into rpc_slot allocation so that the RPC layer
> can fully utilize the negotiated TCP window.
>
> Use a slab cache for rpc_slots. Statically allocate an rpc_xprt rpc_slot slab
> cache using GFP_KERNEL to the RPC_DEF_SLOT_TABLE number of slots at
> rpc_xprt allocation.
>
> Add a dynamic rpc slot allocator to rpc_xprt_ops which is set only for TCP.
> For TCP, trigger a dyamic slot allocation in response to a write_space
> callback which is in turn called when the TCP layer is waiting for buffer space.
>
> Dynamically add a slot at the beginning of the RPC call_transmit state. The slot
> allocator uses GFP_NOWAIT and will return without allocating a slot if
> GFP_NOWAIT allocation fails. This is OK because the write_space callback will
> be called again, and the dynamic slot allocator can retry.
>
> Signed-off-by: Andy Adamson <andros@xxxxxxxxx>
> ---
> include/linux/sunrpc/sched.h | 2 +
> include/linux/sunrpc/xprt.h | 6 +++-
> net/sunrpc/clnt.c | 4 ++
> net/sunrpc/sched.c | 39 ++++++++++++++++++++++
> net/sunrpc/xprt.c | 75 +++++++++++++++++++++++++++++++++++++-----
> net/sunrpc/xprtsock.c | 1 +
> 6 files changed, 117 insertions(+), 10 deletions(-)
>
[...]
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index 9494c37..1b0aa55 100644
> --- a/net/sunrpc/xprt.c
> +++ b/net/sunrpc/xprt.c
> @@ -498,6 +498,7 @@ void xprt_write_space(struct rpc_xprt *xprt)
> dprintk("RPC: write space: waking waiting task on "
> "xprt %p\n", xprt);
> rpc_wake_up_queued_task(&xprt->pending, xprt->snd_task);
> + set_bit(XPRT_WRITE_SPACE, &xprt->state);
> }
> spin_unlock_bh(&xprt->transport_lock);
> }
> @@ -957,6 +958,66 @@ static void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
> spin_unlock(&xprt->reserve_lock);
> }
>
Is the above a potential race as well? I looks possible (if unlikely)
that we'd wake up the task, and it find that XPRT_WRITE_SPACE is still
unset. Would it make more sense to do the set_bit call before waking up
the task?
--
Jeff Layton <jlayton@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
