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List:       fuse-devel
Subject:    Re: [fuse-devel] stat performance on multicore systems: measurements
From:       Miklos Szeredi <miklos () szeredi ! hu>
Date:       2012-07-30 15:21:49
Message-ID: 87y5m1i8aa.fsf () tucsk ! pomaz ! szeredi ! hu
[Download RAW message or body]

Stefan Westerfeld <stefan@space.twc.de> writes:

> The way I think it should work is that the FUSE fs will have different worker
> threads which are bound to one cpu per thread. If two processes running on cpu
> 1 and 3 access the filesystem, FUSE should use a worker thread bound to cpu 1
> to process requests from the userspace process running on cpu 1 and another
> worker thread bound to cpu 3 to process requests from the userspace process
> running on cpu 3.

Does the following patch help?

The wake_up_sync() call should prefer scheduling the woken up task on
the same CPU as the waker.

Thanks,
Miklos


diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 7df2b5e..f67071a 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -237,7 +237,8 @@ static u64 fuse_get_unique(struct fuse_conn *fc)
 	return fc->reqctr;
 }
 
-static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
+static void queue_request(struct fuse_conn *fc, struct fuse_req *req,
+			  bool sync_wakeup)
 {
 	req->in.h.len = sizeof(struct fuse_in_header) +
 		len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
@@ -247,7 +248,10 @@ static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
 		req->waiting = 1;
 		atomic_inc(&fc->num_waiting);
 	}
-	wake_up(&fc->waitq);
+	if (sync_wakeup)
+		wake_up_interruptible_sync(&fc->waitq);
+	else
+		wake_up(&fc->waitq);
 	kill_fasync(&fc->fasync, SIGIO, POLL_IN);
 }
 
@@ -279,7 +283,7 @@ static void flush_bg_queue(struct fuse_conn *fc)
 		list_del(&req->list);
 		fc->active_background++;
 		req->in.h.unique = fuse_get_unique(fc);
-		queue_request(fc, req);
+		queue_request(fc, req, false);
 	}
 }
 
@@ -417,7 +421,7 @@ void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
 		req->out.h.error = -ECONNREFUSED;
 	else {
 		req->in.h.unique = fuse_get_unique(fc);
-		queue_request(fc, req);
+		queue_request(fc, req, true);
 		/* acquire extra reference, since request is still needed
 		   after request_end() */
 		__fuse_get_request(req);
@@ -472,7 +476,7 @@ static int fuse_request_send_notify_reply(struct fuse_conn *fc,
 	req->in.h.unique = unique;
 	spin_lock(&fc->lock);
 	if (fc->connected) {
-		queue_request(fc, req);
+		queue_request(fc, req, true);
 		err = 0;
 	}
 	spin_unlock(&fc->lock);

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