[src/trunk]: src/sys/uvm uvm_pageidlezero: use try-lock to not occupy uvm_fpa...

[rmind <rmind%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0beee6b82af1
branches:  trunk
changeset: 763721:0beee6b82af1
user:      rmind <rmind%NetBSD.org@localhost>
date:      Fri Apr 01 00:47:11 2011 +0000

description:
uvm_pageidlezero: use try-lock to not occupy uvm_fpageqlock, which may
be on demand by other CPUs.  Reduces lock contention in some workloads
on many CPU (8+) systems.

Tested by tls@.

diffstat:

 sys/uvm/uvm_page.c |  19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)

diffs (61 lines):

diff -r de5609f3071a -r 0beee6b82af1 sys/uvm/uvm_page.c
--- a/sys/uvm/uvm_page.c        Fri Apr 01 00:07:34 2011 +0000
+++ b/sys/uvm/uvm_page.c        Fri Apr 01 00:47:11 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_page.c,v 1.171 2011/02/02 17:53:42 chuck Exp $     */
+/*     $NetBSD: uvm_page.c,v 1.172 2011/04/01 00:47:11 rmind Exp $     */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -66,7 +66,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.171 2011/02/02 17:53:42 chuck Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.172 2011/04/01 00:47:11 rmind Exp $");
 
 #include "opt_ddb.h"
 #include "opt_uvmhist.h"
@@ -1716,6 +1716,7 @@
        struct pgfreelist *pgfl, *gpgfl;
        struct uvm_cpu *ucpu;
        int free_list, firstbucket, nextbucket;
+       bool lcont = false;
 
        ucpu = curcpu()->ci_data.cpu_uvm;
        if (!ucpu->page_idle_zero ||
@@ -1723,7 +1724,10 @@
                ucpu->page_idle_zero = false;
                return;
        }
-       mutex_enter(&uvm_fpageqlock);
+       if (!mutex_tryenter(&uvm_fpageqlock)) {
+               /* Contention: let other CPUs to use the lock. */
+               return;
+       }
        firstbucket = ucpu->page_free_nextcolor;
        nextbucket = firstbucket;
        do {
@@ -1735,7 +1739,7 @@
                        gpgfl = &uvm.page_free[free_list];
                        while ((pg = LIST_FIRST(&pgfl->pgfl_buckets[
                            nextbucket].pgfl_queues[PGFL_UNKNOWN])) != NULL) {
-                               if (sched_curcpu_runnable_p()) {
+                               if (lcont || sched_curcpu_runnable_p()) {
                                        goto quit;
                                }
                                LIST_REMOVE(pg, pageq.list); /* global list */
@@ -1773,7 +1777,12 @@
 #endif /* PMAP_PAGEIDLEZERO */
                                pg->flags |= PG_ZERO;
 
-                               mutex_spin_enter(&uvm_fpageqlock);
+                               if (!mutex_tryenter(&uvm_fpageqlock)) {
+                                       lcont = true;
+                                       mutex_spin_enter(&uvm_fpageqlock);
+                               } else {
+                                       lcont = false;
+                               }
                                pg->pqflags = PQ_FREE;
                                LIST_INSERT_HEAD(&gpgfl->pgfl_buckets[
                                    nextbucket].pgfl_queues[PGFL_ZEROS],