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5b80147e0c
Currently if several items of work become available in quick succession, that number of threads (if available) will be woken. By the time some of them wake up another thread that was already cache-warm might have come along and completed the work. Anecdotal evidence suggests as many as 15% of wakes find nothing to do once they get to the point of looking. This patch changes svc_pool_wake_idle_thread() to wake the first thread on the queue but NOT remove it. Subsequent calls will wake the same thread. Once that thread starts it will dequeue itself and after dequeueing some work to do, it will wake the next thread if there is more work ready. This results in a more orderly increase in the number of busy threads. As a bonus, this allows us to reduce locking around the idle queue. svc_pool_wake_idle_thread() no longer needs to take a lock (beyond rcu_read_lock()) as it doesn't manipulate the queue, it just looks at the first item. The thread itself can avoid locking by using the new llist_del_first_this() interface. This will safely remove the thread itself if it is the head. If it isn't the head, it will do nothing. If multiple threads call this concurrently only one will succeed. The others will do nothing, so no corruption can result. If a thread wakes up and finds that it cannot dequeue itself that means either - that it wasn't woken because it was the head of the queue. Maybe the freezer woke it. In that case it can go back to sleep (after trying to freeze of course). - some other thread found there was nothing to do very recently, and placed itself on the head of the queue in front of this thread. It must check again after placing itself there, so it can be deemed to be responsible for any pending work, and this thread can go back to sleep until woken. No code ever tests for busy threads any more. Only each thread itself cares if it is busy. So svc_thread_busy() is no longer needed. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> |
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| .. | ||
| auth_gss | ||
| xprtrdma | ||
| .kunitconfig | ||
| addr.c | ||
| auth.c | ||
| auth_null.c | ||
| auth_tls.c | ||
| auth_unix.c | ||
| backchannel_rqst.c | ||
| cache.c | ||
| clnt.c | ||
| debugfs.c | ||
| fail.h | ||
| Kconfig | ||
| Makefile | ||
| netns.h | ||
| rpc_pipe.c | ||
| rpcb_clnt.c | ||
| sched.c | ||
| socklib.c | ||
| socklib.h | ||
| stats.c | ||
| sunrpc.h | ||
| sunrpc_syms.c | ||
| svc.c | ||
| svc_xprt.c | ||
| svcauth.c | ||
| svcauth_unix.c | ||
| svcsock.c | ||
| sysctl.c | ||
| sysfs.c | ||
| sysfs.h | ||
| timer.c | ||
| xdr.c | ||
| xprt.c | ||
| xprtmultipath.c | ||
| xprtsock.c | ||