From: Dave Hansen <dave.hansen@intel.com>
To: Rik van Riel <riel@surriel.com>,
Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: Re: [PATCH] x86,tlb: update mm_cpumask lazily
Date: Fri, 8 Nov 2024 12:10:47 -0800 [thread overview]
Message-ID: <90f8aaf2-ef9c-4777-b8db-17fc7c6cf41b@intel.com> (raw)
In-Reply-To: <55ada30f76d544a3f700e57a01cb6f6f255581d5.camel@surriel.com>
On 11/8/24 12:07, Rik van Riel wrote:
> On Fri, 2024-11-08 at 12:03 -0800, Dave Hansen wrote:
>> On 11/8/24 11:31, Rik van Riel wrote:
>>> /* Start receiving IPIs and then read tlb_gen (and
>>> LAM below) */
>>> - if (next != &init_mm)
>>> + if (next != &init_mm && !cpumask_test_cpu(cpu,
>>> mm_cpumask(next)))
>>> cpumask_set_cpu(cpu, mm_cpumask(next));
>>> next_tlb_gen = atomic64_read(&next-
>>>> context.tlb_gen);
>> If we're worried about contention on mm_cpumask(), then this hunk
>> makes
>> sense independently of the lazy updating. We might want to take this
>> hunk forward before we do the rest because this seems like a no-
>> brainer.
>>
> If we always clear the CPU in the mm_cpumask when prev != next,
> wouldn't that result in that CPU's bit being clear (and needing
> to be set) for next when prev != next?
>
> What am I missing?
Oh, good point. This is all in the (prev != next) block so yeah, the
bit _has_ to be clear. Silly me.
next prev parent reply other threads:[~2024-11-08 20:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-08 19:31 [PATCH] x86,tlb: update mm_cpumask lazily Rik van Riel
2024-11-08 20:03 ` Dave Hansen
2024-11-08 20:07 ` Rik van Riel
2024-11-08 20:10 ` Dave Hansen [this message]
2024-11-08 20:31 ` Dave Hansen
2024-11-08 20:41 ` Rik van Riel
2024-11-08 20:46 ` Dave Hansen
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