kernel.git/net/sunrpc/sched.c, branch linux-5.18.y

SUNRPC: Handle allocation failure in rpc_new_task()

2022-04-07T20:20:00Z

If the call to rpc_alloc_task() fails, then ensure that the calldata is released, and that rpc_run_task() and rpc_run_bc_task() bail out early. Reported-by: NeilBrown Fixes: 910ad38697d9 ("NFS: Fix memory allocation in rpc_alloc_task()") Signed-off-by: Trond Myklebust

NFS: Fix memory allocation in rpc_alloc_task()

2022-03-22T19:52:55Z

As for rpc_malloc(), we first try allocating from the slab, then fall back to a non-waiting allocation from the mempool. Signed-off-by: Trond Myklebust

NFS: Fix memory allocation in rpc_malloc()

2022-03-22T19:52:55Z

When in a low memory situation, we do want rpciod to kick off direct reclaim in the case where that helps, however we don't want it looping forever in mempool_alloc(). So first try allocating from the slab using GFP_KERNEL | __GFP_NORETRY, and then fall back to a GFP_NOWAIT allocation from the mempool. Ditto for rpc_alloc_task() Signed-off-by: Trond Myklebust

SUNRPC: improve 'swap' handling: scheduling and PF_MEMALLOC

2022-03-13T16:59:35Z

rpc tasks can be marked as RPC_TASK_SWAPPER. This causes GFP_MEMALLOC to be used for some allocations. This is needed in some cases, but not in all where it is currently provided, and in some where it isn't provided. Currently *all* tasks associated with a rpc_client on which swap is enabled get the flag and hence some GFP_MEMALLOC support. GFP_MEMALLOC is provided for ->buf_alloc() but only swap-writes need it. However xdr_alloc_bvec does not get GFP_MEMALLOC - though it often does need it. xdr_alloc_bvec is called while the XPRT_LOCK is held. If this blocks, then it blocks all other queued tasks. So this allocation needs GFP_MEMALLOC for *all* requests, not just writes, when the xprt is used for any swap writes. Similarly, if the transport is not connected, that will block all requests including swap writes, so memory allocations should get GFP_MEMALLOC if swap writes are possible. So with this patch: 1/ we ONLY set RPC_TASK_SWAPPER for swap writes. 2/ __rpc_execute() sets PF_MEMALLOC while handling any task with RPC_TASK_SWAPPER set, or when handling any task that holds the XPRT_LOCKED lock on an xprt used for swap. This removes the need for the RPC_IS_SWAPPER() test in ->buf_alloc handlers. 3/ xprt_prepare_transmit() sets PF_MEMALLOC after locking any task to a swapper xprt. __rpc_execute() will clear it. 3/ PF_MEMALLOC is set for all the connect workers. Reviewed-by: Chuck Lever (for xprtrdma parts) Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust

SUNRPC: remove scheduling boost for "SWAPPER" tasks.

2022-03-13T16:59:35Z

Currently, tasks marked as "swapper" tasks get put to the front of non-priority rpc_queues, and are sorted earlier than non-swapper tasks on the transport's ->xmit_queue. This is pointless as currently *all* tasks for a mount that has swap enabled on *any* file are marked as "swapper" tasks. So the net result is that the non-priority rpc_queues are reverse-ordered (LIFO). This scheduling boost is not necessary to avoid deadlocks, and hurts fairness, so remove it. If there were a need to expedite some requests, the tk_priority mechanism is a more appropriate tool. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust

SUNRPC/call_alloc: async tasks mustn't block waiting for memory

2022-03-13T16:59:35Z

When memory is short, new worker threads cannot be created and we depend on the minimum one rpciod thread to be able to handle everything. So it must not block waiting for memory. mempools are particularly a problem as memory can only be released back to the mempool by an async rpc task running. If all available workqueue threads are waiting on the mempool, no thread is available to return anything. rpc_malloc() can block, and this might cause deadlocks. So check RPC_IS_ASYNC(), rather than RPC_IS_SWAPPER() to determine if blocking is acceptable. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust

SUNRPC: Convert GFP_NOFS to GFP_KERNEL

2022-02-25T23:50:12Z

The sections which should not re-enter the filesystem are already protected with memalloc_nofs_save/restore calls, so it is better to use GFP_KERNEL in these calls to allow better performance for synchronous RPC calls. Signed-off-by: Trond Myklebust

SUNRPC: Trace calls to .rpc_call_done

2021-10-20T22:09:54Z

Introduce a single tracepoint that can replace simple dprintk call sites in upper layer "rpc_call_done" callbacks. Example: kworker/u24:2-1254 [001] 771.026677: rpc_stats_latency: task:00000001@00000002 xid=0x16a6f3c0 rpcbindv2 GETPORT backlog=446 rtt=101 execute=555 kworker/u24:2-1254 [001] 771.026677: rpc_task_call_done: task:00000001@00000002 flags=ASYNC|DYNAMIC|SOFT|SOFTCONN|SENT runstate=RUNNING|ACTIVE status=0 action=rpcb_getport_done kworker/u24:2-1254 [001] 771.026678: rpcb_setport: task:00000001@00000002 status=0 port=20048 Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust

SUNRPC: Per-rpc_clnt task PIDs

2021-10-10T09:05:54Z

The current range of RPC task PIDs is 0..65535. That's not adequate for distinguishing tasks across multiple rpc_clnts running high throughput workloads. To help relieve this situation and to reduce the bottleneck of having a single atomic for assigning all RPC task PIDs, assign task PIDs per rpc_clnt. Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust

SUNRPC: Remove WQ_HIGHPRI from xprtiod

2021-10-04T00:49:05Z

Don't let xprtiod pre-empt softirq. Signed-off-by: Trond Myklebust