From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>,
Michael Kelley <mhklinux@outlook.com>
Cc: Borislav Petkov <bp@alien8.de>, Yury Norov <yury.norov@gmail.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Question about num_possible_cpus() and cpu_possible_mask
Date: Mon, 30 Sep 2024 11:06:21 +0200 [thread overview]
Message-ID: <87msjp1pf6.ffs@tglx> (raw)
In-Reply-To: <20240930075600.GC5594@noisy.programming.kicks-ass.net>
On Mon, Sep 30 2024 at 09:56, Peter Zijlstra wrote:
> On Wed, Sep 25, 2024 at 04:04:33AM +0000, Michael Kelley wrote:
>> Question: Is there any intention to guarantee that the cpu_possible_mask is
>> "dense", in that all bit positions 0 thru (nr_cpu_ids - 1) are set, with no
>> "holes"? If that were true, then num_possible_cpus() would be equal to
>> nr_cpu_ids.
>
> I think we've historically had machines where there were holes in. And I
> think we're wanting to have holes in for modern hybrid x86 that have HT,
> although I'm not entirely sure where those patches are atm.
>
> Thomas, didn't we have a patch that renumbers CPUs for hybrid crud sich
> that HT is always the low bit and we end up with holes because the atoms
> don't have HT on?
>
> Or was that on my plate and it got lost in the giant todo pile?
We talked about it some time ago, but that went nowhere.
Thanks,
tglx
next prev parent reply other threads:[~2024-09-30 9:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-25 4:04 Question about num_possible_cpus() and cpu_possible_mask Michael Kelley
2024-09-30 7:56 ` Peter Zijlstra
2024-09-30 9:06 ` Thomas Gleixner [this message]
2024-09-30 19:33 ` Michael Kelley
2024-09-30 9:16 ` Mark Rutland
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=87msjp1pf6.ffs@tglx \
--to=tglx@linutronix.de \
--cc=bp@alien8.de \
--cc=linux-kernel@vger.kernel.org \
--cc=mhklinux@outlook.com \
--cc=peterz@infradead.org \
--cc=x86@kernel.org \
--cc=yury.norov@gmail.com \
/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