Aren
/
NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Add a comment.

This commit is contained in:
ad 2019-12-11 20:50:32 +00:00
parent 697d97f8ad
commit 0a55e6b767
1 changed files with 12 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
sys/kern/vfs_bio.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vfs_bio.c,v 1.282 2019/12/08 20:35:23 ad Exp $ */
/* $NetBSD: vfs_bio.c,v 1.283 2019/12/11 20:50:32 ad Exp $ */
/*-
* Copyright (c) 2007, 2008, 2009, 2019 The NetBSD Foundation, Inc.
@ -123,7 +123,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.282 2019/12/08 20:35:23 ad Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.283 2019/12/11 20:50:32 ad Exp $");
#ifdef _KERNEL_OPT
#include "opt_bufcache.h"
@ -1145,6 +1145,16 @@ already_queued:
/* Unlock the buffer. */
CLR(bp->b_cflags, BC_AGE|BC_BUSY|BC_NOCACHE);
CLR(bp->b_flags, B_ASYNC);
/*
* Wake only the highest priority waiter on the lock, in order to
* prevent a thundering herd: many LWPs simultaneously awakening and
* competing for the buffer's lock. Testing in 2019 revealed this
* to reduce contention on bufcache_lock tenfold during a kernel
* compile. Elsewhere, when the buffer is changing identity, being
* disposed of, or moving from one list to another, we wake all lock
* requestors.
*/
cv_signal(&bp->b_busy);
if (bp->b_bufsize <= 0)