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From: Andy Lutomirski <luto@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@suse.de>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Nadav Amit <nadav.amit@gmail.com>, Rik van Riel <riel@redhat.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: [PATCH v4 10/10] x86/mm: Try to preserve old TLB entries using PCID
Date: Tue, 18 Jul 2017 10:06:15 -0700	[thread overview]
Message-ID: <CALCETrVyY-Bvh8GkwqpC9eL4D0QnkVEjpYmwvPhTJBa9evwqtQ@mail.gmail.com> (raw)
In-Reply-To: <20170718085341.nlt35dph4oukb4tc@gmail.com>

On Tue, Jul 18, 2017 at 1:53 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Peter Zijlstra <peterz@infradead.org> wrote:
>
>> On Wed, Jul 05, 2017 at 09:04:39AM -0700, Andy Lutomirski wrote:
>> > On Wed, Jul 5, 2017 at 5:18 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>> > > On Thu, Jun 29, 2017 at 08:53:22AM -0700, Andy Lutomirski wrote:
>> > >> @@ -104,18 +140,20 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
>> > >>
>> > >>               /* Resume remote flushes and then read tlb_gen. */
>> > >>               cpumask_set_cpu(cpu, mm_cpumask(next));
>> > >
>> > > Barriers should have a comment... what is being ordered here against
>> > > what?
>> >
>> > How's this comment?
>> >
>> >         /*
>> >          * Resume remote flushes and then read tlb_gen.  We need to do
>> >          * it in this order: any inc_mm_tlb_gen() caller that writes a
>> >          * larger tlb_gen than we read here must see our cpu set in
>> >          * mm_cpumask() so that it will know to flush us.  The barrier
>> >          * here synchronizes with inc_mm_tlb_gen().
>> >          */
>>
>> Slightly confusing, you mean this, right?
>>
>>
>>       cpumask_set_cpu(cpu, mm_cpumask());                     inc_mm_tlb_gen();
>>
>>       MB                                                      MB
>>
>>       next_tlb_gen = atomic64_read(&next->context.tlb_gen);   flush_tlb_others(mm_cpumask());
>>
>>
>> which seems to make sense.
>
> Btw., I'll wait for a v5 iteration before applying this last patch to tip:x86/mm.

I'll send it shortly.  I think I'll also add a patch to factor out the
flush calls a bit more to prepare for Mel's upcoming fix.

>
> Thanks,
>
>         Ingo

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  reply	other threads:[~2017-07-18 17:06 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-29 15:53 [PATCH v4 00/10] PCID and improved laziness Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 01/10] x86/mm: Don't reenter flush_tlb_func_common() Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 02/10] x86/mm: Delete a big outdated comment about TLB flushing Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 03/10] x86/mm: Give each mm TLB flush generation a unique ID Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 04/10] x86/mm: Track the TLB's tlb_gen and update the flushing algorithm Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 05/10] x86/mm: Rework lazy TLB mode and TLB freshness tracking Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 06/10] x86/mm: Stop calling leave_mm() in idle code Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 07/10] x86/mm: Disable PCID on 32-bit kernels Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 08/10] x86/mm: Add nopcid to turn off PCID Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 09/10] x86/mm: Enable CR4.PCIDE on supported systems Andy Lutomirski
2017-06-29 15:53 ` [PATCH v4 10/10] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski
2017-07-03 10:56   ` Thomas Gleixner
2017-07-05 12:18   ` Peter Zijlstra
2017-07-05 16:04     ` Andy Lutomirski
2017-07-05 17:02       ` Peter Zijlstra
2017-07-18  8:53         ` Ingo Molnar
2017-07-18 17:06           ` Andy Lutomirski [this message]
2017-07-05 12:25   ` Peter Zijlstra
2017-07-05 16:10     ` Andy Lutomirski
2017-07-28 13:49       ` Peter Zijlstra
2017-06-30 12:44 ` [PATCH v4 00/10] PCID and improved laziness Matt Fleming
2017-07-11 11:32   ` Matt Fleming
2017-07-11 15:00     ` Andy Lutomirski
2017-07-13 19:36       ` Matt Fleming
2017-07-05  8:56 ` Ingo Molnar
2017-07-05 16:53   ` Linus Torvalds
2017-07-17  9:57   ` Mel Gorman
2017-07-17 15:06     ` Ingo Molnar
2017-07-17 15:56       ` Mel Gorman
     [not found] ` <CALBSrqDW6pGjHxOmzfnkY_KoNeH6F=pTb8-tJ8r-zbu4prw9HQ@mail.gmail.com>
2017-09-12 19:32   ` Sai Praneeth Prakhya
2017-09-12 19:45     ` Andy Lutomirski
2017-09-12 20:28       ` Prakhya, Sai Praneeth
2017-09-13  7:43       ` Ingo Molnar
2017-09-13  7:45         ` Ingo Molnar
2017-09-13  4:14     ` Sai Praneeth Prakhya

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