From: Peter Zijlstra <peterz@infradead.org>
To: Eric Dumazet <edumazet@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Borislav Petkov <bp@suse.de>
Subject: Re: [PATCH] x86/apic: reduce cache line misses in __x2apic_send_IPI_mask()
Date: Thu, 7 Oct 2021 16:06:55 +0200 [thread overview]
Message-ID: <YV7+/0+Q1n67wCF8@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CANn89iKOa+tqerm80vHvHEurc2UxTq_heQuOUE0KnVuJht8AKA@mail.gmail.com>
On Thu, Oct 07, 2021 at 07:04:09AM -0700, Eric Dumazet wrote:
> On Thu, Oct 7, 2021 at 12:29 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Wed, Oct 06, 2021 at 08:17:56PM -0700, Eric Dumazet wrote:
> > > +/* __x2apic_send_IPI_mask() possibly needs to read
> > > + * x86_cpu_to_logical_apicid for all online cpus in a sequential way.
> > > + * Using per cpu variable would cost one cache line per cpu.
> > > + */
> >
> > Broken comment style..
>
> I was not sure and ran checkpatch.pl before submission, but sure.
>
> >
> > > +static u32 x86_cpu_to_logical_apicid[NR_CPUS] __read_mostly;
> >
> > NR_CPUS is really sad, could this at all be dynamically allocated? Say
> > in x2apic_cluster_probe() ?
>
> Good idea, I will try this.
> Hopefully nr_cpu_ids is populated there ?
Lets hope :-), I'm always terminally lost in early bringup. I figure it
should be painfully obvious if it goes wrong.
next prev parent reply other threads:[~2021-10-07 14:08 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-07 3:17 [PATCH] x86/apic: reduce cache line misses in __x2apic_send_IPI_mask() Eric Dumazet
2021-10-07 7:29 ` Peter Zijlstra
2021-10-07 14:04 ` Eric Dumazet
2021-10-07 14:06 ` Peter Zijlstra [this message]
2021-10-07 14:13 ` Eric Dumazet
2021-10-07 22:13 ` Eric Dumazet
2021-10-12 12:45 ` Peter Zijlstra
2021-10-13 18:02 ` Eric Dumazet
2021-10-15 13:26 ` Peter Zijlstra
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=YV7+/0+Q1n67wCF8@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=bp@suse.de \
--cc=dave.hansen@linux.intel.com \
--cc=edumazet@google.com \
--cc=eric.dumazet@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
/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