[src/trunk]: src/sys/external/bsd/common/linux linux: Rate-limit RCU GC threa...

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

details:   https://anonhg.NetBSD.org/src/rev/bdc11ca7f077
branches:  trunk
changeset: 1028994:bdc11ca7f077
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Dec 19 12:40:03 2021 +0000

description:
linux: Rate-limit RCU GC thread as a cheap experiment.

diffstat:

 sys/external/bsd/common/linux/linux_rcu.c |  13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diffs (34 lines):

diff -r 52b6a891da3b -r bdc11ca7f077 sys/external/bsd/common/linux/linux_rcu.c
--- a/sys/external/bsd/common/linux/linux_rcu.c Sun Dec 19 12:39:56 2021 +0000
+++ b/sys/external/bsd/common/linux/linux_rcu.c Sun Dec 19 12:40:03 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_rcu.c,v 1.5 2021/12/19 12:07:55 riastradh Exp $  */
+/*     $NetBSD: linux_rcu.c,v 1.6 2021/12/19 12:40:03 riastradh Exp $  */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_rcu.c,v 1.5 2021/12/19 12:07:55 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_rcu.c,v 1.6 2021/12/19 12:40:03 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -276,6 +276,15 @@
                /* Finished a batch of work.  Notify rcu_barrier.  */
                gc.gen++;
                cv_broadcast(&gc.cv);
+
+               /*
+                * Limit ourselves to one batch per tick, in an attempt
+                * to make the batches larger.
+                *
+                * XXX We should maybe also limit the size of each
+                * batch.
+                */
+               (void)kpause("lxrcubat", /*intr*/false, /*timo*/1, &gc.lock);
        }
        KASSERT(gc.first_callback == NULL);
        KASSERT(gc.first_kfree == NULL);