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Function pserialize_perform() usually succeeds after two cross calls

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so defer kpause() to iterations three and above.

Speeds up VOP_REVOKE() on /proc/XXX/status by a factor of ~12.

Ok: core@
This commit is contained in:
hannken 2018-04-16 20:25:21 +00:00
parent adff91e18b
commit eba426546b
1 changed files with 6 additions and 3 deletions
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9
sys/kern/subr_pserialize.c
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@ -1,4 +1,4 @@
/* $NetBSD: subr_pserialize.c,v 1.10 2017/12/28 03:39:48 msaitoh Exp $ */
/* $NetBSD: subr_pserialize.c,v 1.11 2018/04/16 20:25:21 hannken Exp $ */
/*-
* Copyright (c) 2010, 2011 The NetBSD Foundation, Inc.
@ -38,7 +38,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_pserialize.c,v 1.10 2017/12/28 03:39:48 msaitoh Exp $");
__KERNEL_RCSID(0, "$NetBSD: subr_pserialize.c,v 1.11 2018/04/16 20:25:21 hannken Exp $");
#include <sys/param.h>
@ -146,6 +146,7 @@ pserialize_destroy(pserialize_t psz)
void
pserialize_perform(pserialize_t psz)
{
int n;
uint64_t xc;
KASSERT(!cpu_intr_p());
@ -176,6 +177,7 @@ pserialize_perform(pserialize_t psz)
TAILQ_INSERT_TAIL(&psz_queue0, psz, psz_chain);
psz_work_todo++;
n = 0;
do {
mutex_spin_exit(&psz_lock);
@ -183,9 +185,10 @@ pserialize_perform(pserialize_t psz)
* Force some context switch activity on every CPU, as
* the system may not be busy. Pause to not flood.
*/
if (n++ > 1)
kpause("psrlz", false, 1, NULL);
xc = xc_broadcast(XC_HIGHPRI, (xcfunc_t)nullop, NULL, NULL);
xc_wait(xc);
kpause("psrlz", false, 1, NULL);
mutex_spin_enter(&psz_lock);
} while (!kcpuset_iszero(psz->psz_target));