> On Jan 30, 2017, at 3:29 PM, Anna Schumaker <schumaker.anna@xxxxxxxxx> wrote:
>
> Hi Chuck,
>
> On 01/26/2017 12:56 PM, Chuck Lever wrote:
>> Allow RPC-over-RDMA to send NULL pings even when the transport has
>> hit its credit limit.
>>
>> One credit is reserved. It may be used only to send a keepalive
>> ping.
>>
>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>> ---
>> include/linux/sunrpc/sched.h | 2 ++
>> net/sunrpc/xprt.c | 4 ++++
>> net/sunrpc/xprtrdma/transport.c | 4 +++-
>> net/sunrpc/xprtrdma/verbs.c | 13 ++++++++-----
>> 4 files changed, 17 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
>> index 7ba040c..a65278e 100644
>> --- a/include/linux/sunrpc/sched.h
>> +++ b/include/linux/sunrpc/sched.h
>> @@ -127,6 +127,7 @@ struct rpc_task_setup {
>> #define RPC_TASK_TIMEOUT 0x1000 /* fail with ETIMEDOUT on timeout */
>> #define RPC_TASK_NOCONNECT 0x2000 /* return ENOTCONN if not connected */
>> #define RPC_TASK_NO_RETRANS_TIMEOUT 0x4000 /* wait forever for a reply */
>> +#define RPC_TASK_PRIORITY 0x8000 /* skip congestion control */
>
> This file also defines various RPC_PRIORITY_<whatever> values that get used for the task->tk_priority field. I wonder if there is a better name for this flag that would help keep people from confusing the two later down the line, but I'm also struggling to come up with anything better.
PRIORITY was a (lead) trial balloon, and also a sign of weak imagination.
The point of the flag is to bypass congestion control. RPC_TASK_SKIPCONG ?
Meh.
> Thoughts?
> Anna
>
>>
>> #define RPC_IS_ASYNC(t) ((t)->tk_flags & RPC_TASK_ASYNC)
>> #define RPC_IS_SWAPPER(t) ((t)->tk_flags & RPC_TASK_SWAPPER)
>> @@ -135,6 +136,7 @@ struct rpc_task_setup {
>> #define RPC_IS_SOFT(t) ((t)->tk_flags & (RPC_TASK_SOFT|RPC_TASK_TIMEOUT))
>> #define RPC_IS_SOFTCONN(t) ((t)->tk_flags & RPC_TASK_SOFTCONN)
>> #define RPC_WAS_SENT(t) ((t)->tk_flags & RPC_TASK_SENT)
>> +#define RPC_HAS_PRIORITY(t) ((t)->tk_flags & RPC_TASK_PRIORITY)
>>
>> #define RPC_TASK_RUNNING 0
>> #define RPC_TASK_QUEUED 1
>> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
>> index b530a28..e8b7b9f 100644
>> --- a/net/sunrpc/xprt.c
>> +++ b/net/sunrpc/xprt.c
>> @@ -392,6 +392,10 @@ static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *ta
>> {
>> struct rpc_rqst *req = task->tk_rqstp;
>>
>> + if (RPC_HAS_PRIORITY(task)) {
>> + req->rq_cong = 0;
>> + return 1;
>> + }
>> if (req->rq_cong)
>> return 1;
>> dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu\n",
>> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
>> index f97c851..e43cc85 100644
>> --- a/net/sunrpc/xprtrdma/transport.c
>> +++ b/net/sunrpc/xprtrdma/transport.c
>> @@ -538,7 +538,9 @@ static void rpcrdma_keepalive_release(void *calldata)
>>
>> data = xprt_get(xprt);
>> null_task = rpc_call_null_helper(task->tk_client, xprt, NULL,
>> - RPC_TASK_SOFT | RPC_TASK_ASYNC,
>> + RPC_TASK_SOFT |
>> + RPC_TASK_ASYNC |
>> + RPC_TASK_PRIORITY,
>> &rpcrdma_keepalive_call_ops, data);
>> if (!IS_ERR(null_task))
>> rpc_put_task(null_task);
>> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
>> index 7e14b73..3e218dd 100644
>> --- a/net/sunrpc/xprtrdma/verbs.c
>> +++ b/net/sunrpc/xprtrdma/verbs.c
>> @@ -136,19 +136,20 @@
>> static void
>> rpcrdma_update_granted_credits(struct rpcrdma_rep *rep)
>> {
>> - struct rpcrdma_msg *rmsgp = rdmab_to_msg(rep->rr_rdmabuf);
>> struct rpcrdma_buffer *buffer = &rep->rr_rxprt->rx_buf;
>> + __be32 *p = rep->rr_rdmabuf->rg_base;
>> u32 credits;
>>
>> if (rep->rr_len < RPCRDMA_HDRLEN_ERR)
>> return;
>>
>> - credits = be32_to_cpu(rmsgp->rm_credit);
>> + credits = be32_to_cpup(p + 2);
>> + if (credits > buffer->rb_max_requests)
>> + credits = buffer->rb_max_requests;
>> + /* Reserve one credit for keepalive ping */
>> + credits--;
>> if (credits == 0)
>> credits = 1; /* don't deadlock */
>> - else if (credits > buffer->rb_max_requests)
>> - credits = buffer->rb_max_requests;
>> -
>> atomic_set(&buffer->rb_credits, credits);
>> }
>>
>> @@ -914,6 +915,8 @@ struct rpcrdma_rep *
>> struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
>> int i, rc;
>>
>> + if (r_xprt->rx_data.max_requests < 2)
>> + return -EINVAL;
>> buf->rb_max_requests = r_xprt->rx_data.max_requests;
>> buf->rb_bc_srv_max_requests = 0;
>> atomic_set(&buf->rb_credits, 1);
>>
>> --
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--
Chuck Lever
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