From: Dave Hansen <dave.hansen@intel.com>
To: Peter Zijlstra <peterz@infradead.org>,
Alison Schofield <alison.schofield@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Dave Hansen <dave.hansen@linux.intel.com>,
Tony Luck <tony.luck@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
"H. Peter Anvin" <hpa@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Igor Mammedov <imammedo@redhat.com>,
Prarit Bhargava <prarit@redhat.com>,
brice.goglin@gmail.com
Subject: Re: [PATCH] x86, sched: Allow NUMA nodes to share an LLC on Intel platforms
Date: Wed, 10 Feb 2021 07:22:03 -0800 [thread overview]
Message-ID: <b717d5cd-e40d-c86a-05de-a512a5e3b0af@intel.com> (raw)
In-Reply-To: <YCOTujUj3D53uGjd@hirez.programming.kicks-ass.net>
On 2/10/21 12:05 AM, Peter Zijlstra wrote:
>> + if (IS_ENABLED(CONFIG_NUMA))
>> + set_cpu_bug(c, X86_BUG_NUMA_SHARES_LLC);
>> }
> This seens wrong too, it shouldn't be allowed pre SKX. And ideally only
> be allowed when SNC is enabled.
Originally, this just added a few more models to the list of CPUs with
SNC. I was hoping for something a bit more durable that we wouldn't
have to go back and poke at every year or two.
> Please make this more specific than: all Intel CPUs. Ofcourse, since you
> all knew this was an issue, you could've made it discoverable
> _somewhere_ :-(
You're totally right, of course. The hardware could enumerate SNC as a
feature explicitly somewhere. But, that's a little silly because all of
the information that it's enumerating about the CPU caches and NUMA
nodes present and correct is *correct*. The secondary information would
only be for the CPU to say, "yeah, I'm really sure about that other stuff".
I think this sanity check has outlived its usefulness.
next prev parent reply other threads:[~2021-02-10 15:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 22:39 [PATCH] x86, sched: Allow NUMA nodes to share an LLC on Intel platforms Alison Schofield
2021-02-09 23:09 ` Luck, Tony
2021-02-10 8:10 ` Peter Zijlstra
2021-02-10 17:41 ` Dave Hansen
2021-02-10 8:05 ` Peter Zijlstra
2021-02-10 15:22 ` Dave Hansen [this message]
2021-02-10 19:38 ` Peter Zijlstra
2021-02-10 22:11 ` Alison Schofield
2021-02-16 11:29 ` Peter Zijlstra
2021-02-16 19:53 ` Alison Schofield
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