From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch <linux-arch@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Linux-MM <linux-mm@kvack.org>, Anton Blanchard <anton@ozlabs.org>
Subject: Re: [PATCH 6/8] lazy tlb: shoot lazies, a non-refcounting lazy tlb option
Date: Mon, 30 Nov 2020 10:26:28 +0100 [thread overview]
Message-ID: <20201130092628.GL2414@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CALCETrVXUbe8LfNn-Qs+DzrOQaiw+sFUg1J047yByV31SaTOZw@mail.gmail.com>
On Sat, Nov 28, 2020 at 07:54:57PM -0800, Andy Lutomirski wrote:
> Version (b) seems fairly straightforward to implement -- add RCU
> protection and a atomic_t special_ref_cleared (initially 0) to struct
> mm_struct itself. After anyone clears a bit to mm_cpumask (which is
> already a barrier),
No it isn't. clear_bit() implies no barrier what so ever. That's x86
you're thinking about.
> they read mm_users. If it's zero, then they scan
> mm_cpumask and see if it's empty. If it is, they atomically swap
> special_ref_cleared to 1. If it was zero before the swap, they do
> mmdrop(). I can imagine some tweaks that could make this a big
> faster, at least in the limit of a huge number of CPUs.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: linux-arch <linux-arch@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Linux-MM <linux-mm@kvack.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 6/8] lazy tlb: shoot lazies, a non-refcounting lazy tlb option
Date: Mon, 30 Nov 2020 10:26:28 +0100 [thread overview]
Message-ID: <20201130092628.GL2414@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CALCETrVXUbe8LfNn-Qs+DzrOQaiw+sFUg1J047yByV31SaTOZw@mail.gmail.com>
On Sat, Nov 28, 2020 at 07:54:57PM -0800, Andy Lutomirski wrote:
> Version (b) seems fairly straightforward to implement -- add RCU
> protection and a atomic_t special_ref_cleared (initially 0) to struct
> mm_struct itself. After anyone clears a bit to mm_cpumask (which is
> already a barrier),
No it isn't. clear_bit() implies no barrier what so ever. That's x86
you're thinking about.
> they read mm_users. If it's zero, then they scan
> mm_cpumask and see if it's empty. If it is, they atomically swap
> special_ref_cleared to 1. If it was zero before the swap, they do
> mmdrop(). I can imagine some tweaks that could make this a big
> faster, at least in the limit of a huge number of CPUs.
next prev parent reply other threads:[~2020-11-30 9:27 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-28 16:01 [PATCH 0/8] shoot lazy tlbs Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-28 16:01 ` [PATCH 1/8] lazy tlb: introduce exit_lazy_tlb Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-29 0:38 ` Andy Lutomirski
2020-11-29 0:38 ` Andy Lutomirski
2020-12-02 2:49 ` Nicholas Piggin
2020-12-02 2:49 ` Nicholas Piggin
2020-11-28 16:01 ` [PATCH 2/8] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-28 17:55 ` Andy Lutomirski
2020-11-28 17:55 ` Andy Lutomirski
2020-12-02 2:49 ` Nicholas Piggin
2020-12-02 2:49 ` Nicholas Piggin
2020-12-03 5:09 ` Andy Lutomirski
2020-12-03 5:09 ` Andy Lutomirski
2020-12-05 8:00 ` Nicholas Piggin
2020-12-05 8:00 ` Nicholas Piggin
2020-12-05 16:11 ` Andy Lutomirski
2020-12-05 16:11 ` Andy Lutomirski
2020-12-05 23:14 ` Nicholas Piggin
2020-12-05 23:14 ` Nicholas Piggin
2020-12-06 0:36 ` Andy Lutomirski
2020-12-06 0:36 ` Andy Lutomirski
2020-12-06 3:59 ` Nicholas Piggin
2020-12-06 3:59 ` Nicholas Piggin
2020-12-11 0:11 ` Andy Lutomirski
2020-12-11 0:11 ` Andy Lutomirski
2020-12-14 4:07 ` Nicholas Piggin
2020-12-14 4:07 ` Nicholas Piggin
2020-12-14 5:53 ` Nicholas Piggin
2020-12-14 5:53 ` Nicholas Piggin
2020-11-30 14:57 ` Mathieu Desnoyers
2020-11-30 14:57 ` Mathieu Desnoyers
2020-11-28 16:01 ` [PATCH 3/8] x86: remove ARCH_HAS_SYNC_CORE_BEFORE_USERMODE Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-28 16:01 ` [PATCH 4/8] lazy tlb: introduce lazy mm refcount helper functions Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-28 16:01 ` [PATCH 5/8] lazy tlb: allow lazy tlb mm switching to be configurable Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-29 0:36 ` Andy Lutomirski
2020-11-29 0:36 ` Andy Lutomirski
2020-12-02 2:49 ` Nicholas Piggin
2020-12-02 2:49 ` Nicholas Piggin
2020-11-28 16:01 ` [PATCH 6/8] lazy tlb: shoot lazies, a non-refcounting lazy tlb option Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-29 3:54 ` Andy Lutomirski
2020-11-29 3:54 ` Andy Lutomirski
2020-11-29 20:16 ` Andy Lutomirski
2020-11-29 20:16 ` Andy Lutomirski
2020-11-30 9:25 ` Peter Zijlstra
2020-11-30 9:25 ` Peter Zijlstra
2020-11-30 18:31 ` Andy Lutomirski
2020-11-30 18:31 ` Andy Lutomirski
2020-12-01 21:27 ` Will Deacon
2020-12-01 21:27 ` Will Deacon
2020-12-01 21:50 ` Andy Lutomirski
2020-12-01 21:50 ` Andy Lutomirski
2020-12-01 23:04 ` Will Deacon
2020-12-01 23:04 ` Will Deacon
2020-12-02 3:47 ` Nicholas Piggin
2020-12-02 3:47 ` Nicholas Piggin
2020-12-03 5:05 ` Andy Lutomirski
2020-12-03 5:05 ` Andy Lutomirski
2020-12-03 17:03 ` Alexander Gordeev
2020-12-03 17:03 ` Alexander Gordeev
2020-12-03 17:14 ` Andy Lutomirski
2020-12-03 17:14 ` Andy Lutomirski
2020-12-03 18:33 ` Alexander Gordeev
2020-12-03 18:33 ` Alexander Gordeev
2020-11-30 9:26 ` Peter Zijlstra [this message]
2020-11-30 9:26 ` Peter Zijlstra
2020-11-30 9:30 ` Peter Zijlstra
2020-11-30 9:30 ` Peter Zijlstra
2020-11-30 9:34 ` Peter Zijlstra
2020-11-30 9:34 ` Peter Zijlstra
2020-12-02 3:09 ` Nicholas Piggin
2020-12-02 3:09 ` Nicholas Piggin
2020-12-02 11:17 ` Peter Zijlstra
2020-12-02 11:17 ` Peter Zijlstra
2020-12-02 12:45 ` Peter Zijlstra
2020-12-02 12:45 ` Peter Zijlstra
2020-12-02 14:19 ` Peter Zijlstra
2020-12-02 14:19 ` Peter Zijlstra
2020-12-02 14:38 ` Andy Lutomirski
2020-12-02 14:38 ` Andy Lutomirski
2020-12-02 16:29 ` Peter Zijlstra
2020-12-02 16:29 ` Peter Zijlstra
2020-11-28 16:01 ` [PATCH 7/8] powerpc: use lazy mm refcount helper functions Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
2020-11-28 16:01 ` [PATCH 8/8] powerpc/64s: enable MMU_LAZY_TLB_SHOOTDOWN Nicholas Piggin
2020-11-28 16:01 ` Nicholas Piggin
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