From: Leonardo Bras <leonardo@linux.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>,
Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Will Deacon <will@kernel.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>, Paul Mackerras <paulus@samba.org>,
Thomas Gleixner <tglx@linutronix.de>,
Enrico Weigelt <info@metux.net>,
Allison Randal <allison@lohutok.net>
Subject: Re: [PATCH 1/1] ppc/crash: Skip spinlocks during crash
Date: Mon, 30 Mar 2020 11:12:45 -0300 [thread overview]
Message-ID: <d52b7462dfa5189a9e7590d6db88bc22b8c2ac5d.camel@linux.ibm.com> (raw)
In-Reply-To: <20200330110231.GG20696@hirez.programming.kicks-ass.net>
[-- Attachment #1: Type: text/plain, Size: 677 bytes --]
Hello Peter,
On Mon, 2020-03-30 at 13:02 +0200, Peter Zijlstra wrote:
> do {
> > > + if (unlikely(crash_skip_spinlock))
> > > + return;
> >
> > You are adding a test that reads a global var in the middle of a so hot path
> > ? That must kill performance. Can we do different ?
>
> This; adding code to a super hot patch like this for an exceptional case
> like the crash handling seems like a very very bad trade to me.
>
> One possible solution is to simply write 0 to the affected spinlocks
> after sending the NMI IPI thing, no?
Yes, I agree.
I suggested this on a comment in v2 of this patch:
http://patchwork.ozlabs.org/patch/1262468/
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
prev parent reply other threads:[~2020-03-30 14:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 22:28 [PATCH 1/1] ppc/crash: Skip spinlocks during crash Leonardo Bras
2020-03-26 23:26 ` Leonardo Bras
2020-03-27 6:50 ` Christophe Leroy
2020-03-27 15:51 ` Leonardo Bras
2020-03-28 10:19 ` Christophe Leroy
2020-03-30 14:33 ` Leonardo Bras
2020-03-30 11:02 ` Peter Zijlstra
2020-03-30 14:12 ` Leonardo Bras [this message]
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=d52b7462dfa5189a9e7590d6db88bc22b8c2ac5d.camel@linux.ibm.com \
--to=leonardo@linux.ibm.com \
--cc=allison@lohutok.net \
--cc=christophe.leroy@c-s.fr \
--cc=info@metux.net \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mingo@redhat.com \
--cc=paulus@samba.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=will@kernel.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).