From: Andrew Morton <akpm@linux-foundation.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Anton Blanchard <anton@ozlabs.org>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
Andy Lutomirski <luto@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v4 1/4] lazy tlb: introduce lazy mm refcount helper functions
Date: Mon, 7 Jun 2021 18:48:05 -0700 [thread overview]
Message-ID: <20210607184805.eddf8eb26b80e8af85d5777e@linux-foundation.org> (raw)
In-Reply-To: <1623116020.vyls9ehp49.astroid@bobo.none>
On Tue, 08 Jun 2021 11:39:56 +1000 Nicholas Piggin <npiggin@gmail.com> wrote:
> > Looks like a functional change. What's happening here?
>
> That's kthread_use_mm being clever about the lazy tlb mm. If it happened
> that the kthread had inherited a the lazy tlb mm that happens to be the
> one we want to use here, then we already have a refcount to it via the
> lazy tlb ref.
>
> So then it doesn't have to touch the refcount, but rather just converts
> it from the lazy tlb ref to the returned reference. If the lazy tlb mm
> doesn't get a reference, we can't do that.
Please cover this in the changelog and perhaps a code comment.
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linux-arch@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andy Lutomirski <luto@kernel.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v4 1/4] lazy tlb: introduce lazy mm refcount helper functions
Date: Mon, 7 Jun 2021 18:48:05 -0700 [thread overview]
Message-ID: <20210607184805.eddf8eb26b80e8af85d5777e@linux-foundation.org> (raw)
In-Reply-To: <1623116020.vyls9ehp49.astroid@bobo.none>
On Tue, 08 Jun 2021 11:39:56 +1000 Nicholas Piggin <npiggin@gmail.com> wrote:
> > Looks like a functional change. What's happening here?
>
> That's kthread_use_mm being clever about the lazy tlb mm. If it happened
> that the kthread had inherited a the lazy tlb mm that happens to be the
> one we want to use here, then we already have a refcount to it via the
> lazy tlb ref.
>
> So then it doesn't have to touch the refcount, but rather just converts
> it from the lazy tlb ref to the returned reference. If the lazy tlb mm
> doesn't get a reference, we can't do that.
Please cover this in the changelog and perhaps a code comment.
next prev parent reply other threads:[~2021-06-08 1:48 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-05 1:42 [PATCH v4 0/4] shoot lazy tlbs Nicholas Piggin
2021-06-05 1:42 ` Nicholas Piggin
2021-06-05 1:42 ` [PATCH v4 1/4] lazy tlb: introduce lazy mm refcount helper functions Nicholas Piggin
2021-06-05 1:42 ` Nicholas Piggin
2021-06-07 23:49 ` Andrew Morton
2021-06-07 23:49 ` Andrew Morton
2021-06-08 1:39 ` Nicholas Piggin
2021-06-08 1:39 ` Nicholas Piggin
2021-06-08 1:48 ` Andrew Morton [this message]
2021-06-08 1:48 ` Andrew Morton
2021-06-08 4:11 ` Nicholas Piggin
2021-06-08 4:11 ` Nicholas Piggin
2021-06-05 1:42 ` [PATCH v4 2/4] lazy tlb: allow lazy tlb mm refcounting to be configurable Nicholas Piggin
2021-06-05 1:42 ` Nicholas Piggin
2021-06-08 3:11 ` Nicholas Piggin
2021-06-08 3:11 ` Nicholas Piggin
2021-06-08 16:20 ` Andy Lutomirski
2021-06-08 16:20 ` Andy Lutomirski
2021-06-14 0:45 ` Nicholas Piggin
2021-06-14 0:45 ` Nicholas Piggin
2021-06-14 3:52 ` Andy Lutomirski
2021-06-14 3:52 ` Andy Lutomirski
2021-06-14 4:14 ` Nicholas Piggin
2021-06-14 4:14 ` Nicholas Piggin
2021-06-14 4:47 ` Nicholas Piggin
2021-06-14 4:47 ` Nicholas Piggin
2021-06-14 5:21 ` Nicholas Piggin
2021-06-14 5:21 ` Nicholas Piggin
2021-06-14 16:20 ` Andy Lutomirski
2021-06-14 16:20 ` Andy Lutomirski
2021-06-15 0:55 ` Nicholas Piggin
2021-06-15 0:55 ` Nicholas Piggin
2021-06-16 0:14 ` Andy Lutomirski
2021-06-16 0:14 ` Andy Lutomirski
2021-06-16 1:02 ` Nicholas Piggin
2021-06-16 1:02 ` Nicholas Piggin
2021-06-17 0:32 ` Nicholas Piggin
2021-06-17 0:32 ` Nicholas Piggin
2021-06-05 1:42 ` [PATCH v4 3/4] lazy tlb: shoot lazies, a non-refcounting lazy tlb option Nicholas Piggin
2021-06-05 1:42 ` Nicholas Piggin
2021-06-08 3:15 ` Nicholas Piggin
2021-06-08 3:15 ` Nicholas Piggin
2021-06-05 1:42 ` [PATCH v4 4/4] powerpc/64s: enable MMU_LAZY_TLB_SHOOTDOWN Nicholas Piggin
2021-06-05 1:42 ` Nicholas Piggin
2021-06-07 23:52 ` Andrew Morton
2021-06-07 23:52 ` Andrew Morton
2021-06-08 2:13 ` Nicholas Piggin
2021-06-08 2:13 ` Nicholas Piggin
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