From: Nadav Amit <namit@vmware.com>
To: Barry Song <21cnbao@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>, X86 ML <x86@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>, Arnd Bergmann <arnd@arndb.de>,
LKML <linux-kernel@vger.kernel.org>,
"darren@os.amperecomputing.com" <darren@os.amperecomputing.com>,
"yangyicong@hisilicon.com" <yangyicong@hisilicon.com>,
"huzhanyuan@oppo.com" <huzhanyuan@oppo.com>,
"lipeifeng@oppo.com" <lipeifeng@oppo.com>,
"zhangshiming@oppo.com" <zhangshiming@oppo.com>,
"guojian@oppo.com" <guojian@oppo.com>,
"realmz6@gmail.com" <realmz6@gmail.com>,
Barry Song <v-songbaohua@oppo.com>, Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush
Date: Fri, 8 Jul 2022 06:36:47 +0000 [thread overview]
Message-ID: <67943544-6DAA-4C8A-A04D-029D2D36C318@vmware.com> (raw)
In-Reply-To: <20220707125242.425242-3-21cnbao@gmail.com>
On Jul 7, 2022, at 5:52 AM, Barry Song <21cnbao@gmail.com> wrote:
> From: Barry Song <v-songbaohua@oppo.com>
>
> Platforms like ARM64 have hareware TLB shootdown broadcast. They
> don't maintain mm_cpumask and they just send tlbi and related
> sync instructions for TLB flush.
> So if mm_cpumask is empty, we also allow deferred TLB flush
>
> Cc: Nadav Amit <namit@vmware.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>>
> ---
> mm/rmap.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 5bcb334cd6f2..d320c29a4ad8 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -692,8 +692,13 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
> if (!(flags & TTU_BATCH_FLUSH))
> return false;
>
> - /* If remote CPUs need to be flushed then defer batch the flush */
> - if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
> + /*
> + * If remote CPUs need to be flushed then defer batch the flush;
> + * If ARCHs like ARM64 have hardware TLB flush broadcast, thus
> + * they don't maintain mm_cpumask() at all, defer batch as well.
> + */
> + if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids ||
> + cpumask_empty(mm_cpumask(mm)))
The cpumask_empty() is indeed just another memory access, which is most
likely ok. But wouldn’t adding something like CONFIG_ARCH_HAS_MM_CPUMASK
make the code simpler and (slightly, certainly slightly) more performant?
next prev parent reply other threads:[~2022-07-08 6:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 12:52 [PATCH 0/4] mm: arm64: bring up BATCHED_UNMAP_TLB_FLUSH Barry Song
2022-07-07 12:52 ` [PATCH 1/4] Revert "Documentation/features: mark BATCHED_UNMAP_TLB_FLUSH doesn't apply to ARM64" Barry Song
2022-07-07 12:52 ` [PATCH 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush Barry Song
2022-07-08 6:36 ` Nadav Amit [this message]
2022-07-08 6:59 ` Barry Song
2022-07-08 8:08 ` Nadav Amit
2022-07-08 8:17 ` Barry Song
2022-07-08 8:27 ` Peter Zijlstra
2022-07-11 0:30 ` Barry Song
2022-07-07 12:52 ` [PATCH 3/4] mm: rmap: Extend tlbbatch APIs to fit new platforms Barry Song
2022-07-07 16:43 ` Dave Hansen
2022-07-07 21:12 ` Barry Song
2022-07-07 12:52 ` [PATCH 4/4] arm64: support batched/deferred tlb shootdown during page reclamation Barry Song
2022-07-07 13:49 ` Peter Zijlstra
2022-07-07 21:10 ` Barry Song
2022-07-08 6:21 ` Yicong Yang
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