Change the sf_bufs wakeups to be wakeup_one(), because we don't want to

wakeup all of the sleeping threads when we free only one buffer. This
avoids us having to needlessly try again (and fail, and go back to
sleep) for all the threads sleeping. We will now only wakeup the
thread we know will succeed.

Reviewed by: green

1 files changed, 5 insertions, 4 deletions

diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 8cfbf80b785f..e3edad8e1f13 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -95,7 +95,7 @@ static struct {
 
 static vm_offset_t sf_base;
 static struct sf_buf *sf_bufs;
-static int sf_buf_alloc_want;
+static u_int sf_buf_alloc_want;
 
 /*
  * System call interface to the socket abstraction.
@@ -1345,6 +1345,7 @@ sf_buf_init(void *arg)
 		sf_bufs[i].kva = sf_base + i * PAGE_SIZE;
 		SLIST_INSERT_HEAD(&sf_freelist, &sf_bufs[i], free_list);
 	}
+	sf_buf_alloc_want = 0;
 	mtx_exit(&sf_freelist.sf_lock, MTX_DEF);
 }
 
@@ -1358,7 +1359,7 @@ sf_buf_alloc()
 
 	mtx_enter(&sf_freelist.sf_lock, MTX_DEF);
 	while ((sf = SLIST_FIRST(&sf_freelist)) == NULL) {
-		sf_buf_alloc_want = 1;
+		sf_buf_alloc_want++;
 		msleep(&sf_freelist, &sf_freelist.sf_lock, PVM, "sfbufa", 0);
 	}
 	SLIST_REMOVE_HEAD(&sf_freelist, free_list);
@@ -1395,8 +1396,8 @@ sf_buf_free(caddr_t addr, void *args)
 	mtx_enter(&sf_freelist.sf_lock, MTX_DEF);
 	SLIST_INSERT_HEAD(&sf_freelist, sf, free_list);
 	if (sf_buf_alloc_want) {
-		sf_buf_alloc_want = 0;
-		wakeup(&sf_freelist);
+		sf_buf_alloc_want--;
+		wakeup_one(&sf_freelist);
 	}
 	mtx_exit(&sf_freelist.sf_lock, MTX_DEF);
 }