linuxppc-dev.lists.ozlabs.org archive mirror
 help / color / mirror / Atom feed
From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>, Paul Mackerras <paulus@samba.org>
Subject: [PATCH 3/6] powerpc/watchdog: Moderate touch_nmi_watchdog overhead
Date: Wed,  9 Aug 2017 22:41:23 +1000	[thread overview]
Message-ID: <20170809124126.28907-4-npiggin@gmail.com> (raw)
In-Reply-To: <20170809124126.28907-1-npiggin@gmail.com>

Some code can go into a tight loop calling touch_nmi_watchdog (e.g.,
stop_machine CPU hotplug code). This can cause contention on watchdog
locks particularly if all CPUs with watchdog enabled are spinning in
the loops.

Avoid this storm of activity by running the watchdog timer callback
from this path if we have exceeded the timer period since it was last
run.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/watchdog.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 3a26c3401acc..2806383d2339 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -266,9 +266,11 @@ static void wd_timer_fn(unsigned long data)
 
 void arch_touch_nmi_watchdog(void)
 {
+	unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
 	int cpu = smp_processor_id();
 
-	watchdog_timer_interrupt(cpu);
+	if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
+		watchdog_timer_interrupt(cpu);
 }
 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 
-- 
2.13.3

  parent reply	other threads:[~2017-08-09 12:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-09 12:41 [PATCH 0/6] watchdog and NMI IPI locking improvements Nicholas Piggin
2017-08-09 12:41 ` [PATCH 1/6] powerpc: NMI IPI improve lock primitive Nicholas Piggin
2017-08-10 12:07   ` [1/6] " Michael Ellerman
2017-08-09 12:41 ` [PATCH 2/6] powerpc/watchdog: Improve watchdog " Nicholas Piggin
2017-08-09 12:41 ` Nicholas Piggin [this message]
2017-08-09 12:41 ` [PATCH 4/6] powerpc/watchdog: Fix final-check recovered case Nicholas Piggin
2017-08-09 12:41 ` [PATCH 5/6] powerpc/watchdog: Fix marking of stuck CPUs Nicholas Piggin
2017-08-09 12:41 ` [PATCH 6/6] powerpc/watchdog: add locking around init/exit functions Nicholas Piggin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170809124126.28907-4-npiggin@gmail.com \
    --to=npiggin@gmail.com \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=paulus@samba.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).