From: Andy Lutomirski <luto@amacapital.net>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, LKML <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Christoph Hellwig <hch@lst.de>,
Matthew Wilcox <willy@infradead.org>,
Daniel Vetter <daniel@ffwll.ch>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>, Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: [patch V4 4/8] sched: Make migrate_disable/enable() independent of RT
Date: Mon, 23 Nov 2020 14:07:19 -0800 [thread overview]
Message-ID: <9BAD6F21-4DB5-4277-A38D-BB1FA038F2D7@amacapital.net> (raw)
In-Reply-To: <87h7pfn4u3.fsf@nanos.tec.linutronix.de>
> On Nov 23, 2020, at 1:25 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Mon, Nov 23 2020 at 22:15, Thomas Gleixner wrote:
>>> On Sun, Nov 22 2020 at 15:16, Andy Lutomirski wrote:
>>>> On Fri, Nov 20, 2020 at 1:29 AM Peter Zijlstra <peterz@infradead.org> wrote:
>>> The common case of a CPU switching back and forth between a small
>>> number of mms would have no significant overhead.
>>
>> For CPUs which do not support PCID this sucks, which is everything pre
>> Westmere and all of 32bit. Yes, 32bit. If we go there then 32bit has to
>> bite the bullet and use the very same mechanism. Not that I care much
>> TBH.
>
> Bah, I completely forgot that AMD does not support PCID before Zen3
> which is a major showstopper.
Why? Couldn’t we rig up the code so we still track all the ASIDs even if there is no CPU support? We would take the TLB flush hit on every context switch, but we pay that cost anyway. We would avoid the extra copy in the same cases in which we would avoid it if we had PCID.
>
> Thanks,
>
> tglx
next prev parent reply other threads:[~2020-11-23 22:07 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 19:48 [patch V4 0/8] mm/highmem: Preemptible variant of kmap_atomic & friends Thomas Gleixner
2020-11-18 19:48 ` [patch V4 1/8] mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 2/8] mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP Thomas Gleixner
2020-11-18 21:13 ` Linus Torvalds
2020-11-19 8:46 ` Mel Gorman
2020-11-19 17:19 ` Linus Torvalds
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 3/8] x86: Support kmap_local() forced debugging Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2021-01-06 23:01 ` [BUG] from " Steven Rostedt
2021-01-07 1:03 ` Linus Torvalds
2021-01-07 1:16 ` Steven Rostedt
2021-01-07 1:49 ` Steven Rostedt
2021-01-07 1:49 ` Jakub Kicinski
2021-01-07 2:11 ` Willem de Bruijn
2021-01-07 4:44 ` Willem de Bruijn
2021-01-07 19:47 ` Linus Torvalds
2021-01-07 20:52 ` Steven Rostedt
2021-01-07 21:07 ` Willem de Bruijn
2020-11-18 19:48 ` [patch V4 4/8] sched: Make migrate_disable/enable() independent of RT Thomas Gleixner
2020-11-19 9:38 ` Mel Gorman
2020-11-19 11:14 ` Peter Zijlstra
2020-11-19 12:14 ` Mel Gorman
2020-11-19 14:17 ` Steven Rostedt
2020-11-19 17:23 ` Linus Torvalds
2020-11-19 18:28 ` Peter Zijlstra
2020-11-20 1:33 ` Thomas Gleixner
2020-11-20 9:29 ` Peter Zijlstra
2020-11-22 23:16 ` Andy Lutomirski
2020-11-23 21:15 ` Thomas Gleixner
2020-11-23 21:25 ` Thomas Gleixner
2020-11-23 22:07 ` Andy Lutomirski [this message]
2020-11-23 23:10 ` Thomas Gleixner
2020-11-24 10:29 ` [tip: sched/core] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 5/8] sched: highmem: Store local kmaps in task struct Thomas Gleixner
2020-11-19 11:33 ` Peter Zijlstra
2020-11-19 11:51 ` Peter Zijlstra
2020-11-19 12:12 ` Peter Zijlstra
2020-11-19 14:11 ` Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 6/8] mm/highmem: Provide kmap_local* Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 7/8] io-mapping: Provide iomap_local variant Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-18 19:48 ` [patch V4 8/8] x86/crashdump/32: Simplify copy_oldmem_page() Thomas Gleixner
2020-11-24 14:20 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-24 8:03 ` [patch V4 0/8] mm/highmem: Preemptible variant of kmap_atomic & friends Peter Zijlstra
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