Author: kib
Date: Thu Nov 26 18:00:26 2020
New Revision: 368073
URL: https://svnweb.freebsd.org/changeset/base/368073
Log:
Make max ticks for pause in vn_lock_pair() adjustable at runtime.
Reduce default value from hz / 10 to hz / 100.
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/kern/subr_param.c
head/sys/kern/vfs_vnops.c
head/sys/sys/vnode.h
Modified: head/sys/kern/subr_param.c
==============================================================================
--- head/sys/kern/subr_param.c Thu Nov 26 17:39:51 2020 (r368072)
+++ head/sys/kern/subr_param.c Thu Nov 26 18:00:26 2020 (r368073)
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
#include <sys/msgbuf.h>
#include <sys/sysctl.h>
#include <sys/proc.h>
+#include <sys/vnode.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
@@ -183,6 +184,10 @@ init_param1(void)
* sign problems sooner.
*/
ticks = INT_MAX - (hz * 10 * 60);
+
+ vn_lock_pair_pause_max = hz / 100;
+ if (vn_lock_pair_pause_max == 0)
+ vn_lock_pair_pause_max = 1;
#ifdef VM_SWZONE_SIZE_MAX
maxswzone = VM_SWZONE_SIZE_MAX;
Modified: head/sys/kern/vfs_vnops.c
==============================================================================
--- head/sys/kern/vfs_vnops.c Thu Nov 26 17:39:51 2020 (r368072)
+++ head/sys/kern/vfs_vnops.c Thu Nov 26 18:00:26 2020 (r368073)
@@ -3332,11 +3332,16 @@ SYSCTL_ULONG(_debug, OID_AUTO, vn_lock_pair_pause, CTL
&vn_lock_pair_pause_cnt, 0,
"Count of vn_lock_pair deadlocks");
+u_int vn_lock_pair_pause_max;
+SYSCTL_UINT(_debug, OID_AUTO, vn_lock_pair_pause_max, CTLFLAG_RW,
+ &vn_lock_pair_pause_max, 0,
+ "Max ticks for vn_lock_pair deadlock avoidance sleep");
+
static void
vn_lock_pair_pause(const char *wmesg)
{
atomic_add_long(&vn_lock_pair_pause_cnt, 1);
- pause(wmesg, prng32_bounded(hz / 10));
+ pause(wmesg, prng32_bounded(vn_lock_pair_pause_max));
}
/*
Modified: head/sys/sys/vnode.h
==============================================================================
--- head/sys/sys/vnode.h Thu Nov 26 17:39:51 2020 (r368072)
+++ head/sys/sys/vnode.h Thu Nov 26 18:00:26 2020 (r368073)
@@ -448,6 +448,8 @@ extern u_long desiredvnodes; /* number of
vnodes desi
extern struct uma_zone *namei_zone;
extern struct vattr va_null; /* predefined null vattr structure */
+extern u_int vn_lock_pair_pause_max;
+
#define VI_LOCK(vp) mtx_lock(&(vp)->v_interlock)
#define VI_LOCK_FLAGS(vp, flags) mtx_lock_flags(&(vp)->v_interlock,
(flags))
#define VI_TRYLOCK(vp) mtx_trylock(&(vp)->v_interlock)
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