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Make max ticks for pause in vn_lock_pair() adjustable at runtime.

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Reduce default value from hz / 10 to hz / 100.

Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Konstantin Belousov 2020-11-26 18:00:26 +00:00
parent 50696a6e8c
commit 3b1f974bfb
3 changed files with 13 additions and 1 deletions
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5
sys/kern/subr_param.c
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@ -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>
@ -184,6 +185,10 @@ init_param1(void)
*/
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;
#endif

7
sys/kern/vfs_vnops.c
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@ -3332,11 +3332,16 @@ SYSCTL_ULONG(_debug, OID_AUTO, vn_lock_pair_pause, CTLFLAG_RD,
&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));
}
/*

2
sys/sys/vnode.h
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@ -448,6 +448,8 @@ extern u_long desiredvnodes; /* number of vnodes desired */
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)