| Message ID | 1706643505-31122-1-git-send-email-dai.ngo@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/1] SUNRPC: increase size of rpc_wait_queue.qlen from unsigned short to unsigned int | expand |
On Tue, 2024-01-30 at 11:38 -0800, Dai Ngo wrote: > When the NFS client is under extreme load the rpc_wait_queue.qlen counter > can be overflowed. Here is an instant of the backlog queue overflow in a > real world environment shown by drgn helper: > > rpc_task_stats(rpc_clnt): > ------------------------- > rpc_clnt: 0xffff92b65d2bae00 > rpc_xprt: 0xffff9275db64f000 > Queue: sending[64887] pending[524] backlog[30441] binding[0] > XMIT task: 0xffff925c6b1d8e98 > WRITE: 750654 > __dta_call_status_580: 65463 > __dta_call_transmit_status_579: 1 > call_reserveresult: 685189 > nfs_client_init_is_complete: 1 > COMMIT: 584 > call_reserveresult: 573 > __dta_call_status_580: 11 > ACCESS: 1 > __dta_call_status_580: 1 > GETATTR: 10 > __dta_call_status_580: 4 > call_reserveresult: 6 > 751249 tasks for server 111.222.333.444 > Total tasks: 751249 > > count_rpc_wait_queues(xprt): > ---------------------------- > **** rpc_xprt: 0xffff9275db64f000 num_reqs: 65511 > wait_queue: xprt_binding[0] cnt: 0 > wait_queue: xprt_binding[1] cnt: 0 > wait_queue: xprt_binding[2] cnt: 0 > wait_queue: xprt_binding[3] cnt: 0 > rpc_wait_queue[xprt_binding].qlen: 0 maxpriority: 0 > wait_queue: xprt_sending[0] cnt: 0 > wait_queue: xprt_sending[1] cnt: 64887 > wait_queue: xprt_sending[2] cnt: 0 > wait_queue: xprt_sending[3] cnt: 0 > rpc_wait_queue[xprt_sending].qlen: 64887 maxpriority: 3 > wait_queue: xprt_pending[0] cnt: 524 > wait_queue: xprt_pending[1] cnt: 0 > wait_queue: xprt_pending[2] cnt: 0 > wait_queue: xprt_pending[3] cnt: 0 > rpc_wait_queue[xprt_pending].qlen: 524 maxpriority: 0 > wait_queue: xprt_backlog[0] cnt: 0 > wait_queue: xprt_backlog[1] cnt: 685801 > wait_queue: xprt_backlog[2] cnt: 0 > wait_queue: xprt_backlog[3] cnt: 0 > rpc_wait_queue[xprt_backlog].qlen: 30441 maxpriority: 3 [task cnt mismatch] > > There is no effect on operations when this overflow occurs. However > it causes confusion when trying to diagnose the performance problem. > > Signed-off-by: Dai Ngo <dai.ngo@oracle.com> > --- > include/linux/sunrpc/sched.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h > index 8ada7dc802d3..8f9bee0e21c3 100644 > --- a/include/linux/sunrpc/sched.h > +++ b/include/linux/sunrpc/sched.h > @@ -186,7 +186,7 @@ struct rpc_wait_queue { > unsigned char maxpriority; /* maximum priority (0 if queue is not a priority queue) */ > unsigned char priority; /* current priority */ > unsigned char nr; /* # tasks remaining for cookie */ > - unsigned short qlen; /* total # tasks waiting in queue */ > + unsigned int qlen; /* total # tasks waiting in queue */ > struct rpc_timer timer_list; > #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS) > const char * name; Seems fine to me. In fact, on x86_64 there is a 2 byte hole after the existing 2 byte qlen, so this probably won't even result in the structure growing. Reviewed-by: Jeff Layton <jlayton@kernel.org>
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h index 8ada7dc802d3..8f9bee0e21c3 100644 --- a/include/linux/sunrpc/sched.h +++ b/include/linux/sunrpc/sched.h @@ -186,7 +186,7 @@ struct rpc_wait_queue { unsigned char maxpriority; /* maximum priority (0 if queue is not a priority queue) */ unsigned char priority; /* current priority */ unsigned char nr; /* # tasks remaining for cookie */ - unsigned short qlen; /* total # tasks waiting in queue */ + unsigned int qlen; /* total # tasks waiting in queue */ struct rpc_timer timer_list; #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS) const char * name;
When the NFS client is under extreme load the rpc_wait_queue.qlen counter can be overflowed. Here is an instant of the backlog queue overflow in a real world environment shown by drgn helper: rpc_task_stats(rpc_clnt): ------------------------- rpc_clnt: 0xffff92b65d2bae00 rpc_xprt: 0xffff9275db64f000 Queue: sending[64887] pending[524] backlog[30441] binding[0] XMIT task: 0xffff925c6b1d8e98 WRITE: 750654 __dta_call_status_580: 65463 __dta_call_transmit_status_579: 1 call_reserveresult: 685189 nfs_client_init_is_complete: 1 COMMIT: 584 call_reserveresult: 573 __dta_call_status_580: 11 ACCESS: 1 __dta_call_status_580: 1 GETATTR: 10 __dta_call_status_580: 4 call_reserveresult: 6 751249 tasks for server 111.222.333.444 Total tasks: 751249 count_rpc_wait_queues(xprt): ---------------------------- **** rpc_xprt: 0xffff9275db64f000 num_reqs: 65511 wait_queue: xprt_binding[0] cnt: 0 wait_queue: xprt_binding[1] cnt: 0 wait_queue: xprt_binding[2] cnt: 0 wait_queue: xprt_binding[3] cnt: 0 rpc_wait_queue[xprt_binding].qlen: 0 maxpriority: 0 wait_queue: xprt_sending[0] cnt: 0 wait_queue: xprt_sending[1] cnt: 64887 wait_queue: xprt_sending[2] cnt: 0 wait_queue: xprt_sending[3] cnt: 0 rpc_wait_queue[xprt_sending].qlen: 64887 maxpriority: 3 wait_queue: xprt_pending[0] cnt: 524 wait_queue: xprt_pending[1] cnt: 0 wait_queue: xprt_pending[2] cnt: 0 wait_queue: xprt_pending[3] cnt: 0 rpc_wait_queue[xprt_pending].qlen: 524 maxpriority: 0 wait_queue: xprt_backlog[0] cnt: 0 wait_queue: xprt_backlog[1] cnt: 685801 wait_queue: xprt_backlog[2] cnt: 0 wait_queue: xprt_backlog[3] cnt: 0 rpc_wait_queue[xprt_backlog].qlen: 30441 maxpriority: 3 [task cnt mismatch] There is no effect on operations when this overflow occurs. However it causes confusion when trying to diagnose the performance problem. Signed-off-by: Dai Ngo <dai.ngo@oracle.com> --- include/linux/sunrpc/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)