From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Barry Song <21cnbao@gmail.com>
Cc: Yicong Yang <yangyicong@huawei.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org, x86@kernel.org,
catalin.marinas@arm.com, will@kernel.org,
linux-doc@vger.kernel.org, corbet@lwn.net, peterz@infradead.org,
arnd@arndb.de, linux-kernel@vger.kernel.org,
darren@os.amperecomputing.com, yangyicong@hisilicon.com,
huzhanyuan@oppo.com, lipeifeng@oppo.com, zhangshiming@oppo.com,
guojian@oppo.com, realmz6@gmail.com, linux-mips@vger.kernel.org,
openrisc@lists.librecores.org, linuxppc-dev@lists.ozlabs.org,
linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
wangkefeng.wang@huawei.com, xhao@linux.alibaba.com,
prime.zeng@hisilicon.com, Barry Song <v-songbaohua@oppo.com>,
Nadav Amit <namit@vmware.com>, Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH v3 4/4] arm64: support batched/deferred tlb shootdown during page reclamation
Date: Tue, 20 Sep 2022 14:15:34 +0530 [thread overview]
Message-ID: <8c4f103b-8f04-d0ad-b30a-2db7e52b36a3@arm.com> (raw)
In-Reply-To: <CAGsJ_4ywwFJFi+q3Ra5UE3twzS9eExtvuXgoGK-8u4c1ZdXCBw@mail.gmail.com>
On 9/20/22 09:09, Barry Song wrote:
> On Tue, Sep 20, 2022 at 3:00 PM Anshuman Khandual
> <anshuman.khandual@arm.com> wrote:
>>
>>
>> On 8/22/22 13:51, Yicong Yang wrote:
>>> +static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm)
>>> +{
>>> + return true;
>>> +}
>>
>> This needs to be conditional on systems, where there will be performance
>> improvements, and should not just be enabled all the time on all systems.
>> num_online_cpus() > X, which does not hold any cpu hotplug lock would be
>> a good metric ?
>
> for a small system, i don't see how this patch will help, e.g. cpus <= 4;
> so we can actually disable tlb-batch on small systems.
Do not subscribe ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH based on NR_CPUS ?
That might not help much as the default value is 256 for NR_CPUS.
OR
arch_tlbbatch_should_defer() checks on
1. online cpus (dont enable batched TLB if <= X)
2. ARM64_WORKAROUND_REPEAT_TLBI (dont enable batched TLB)
> just need to check if we will have any race condition since hotplug will
> make the condition true and false dynamically.
If should_defer_flush() evaluate to be false, then ptep_clear_flush()
clears and flushes the entry right away. This should not race with other
queued up TLBI requests, which will be flushed separately. Wondering how
there can be a race here !
next prev parent reply other threads:[~2022-09-20 8:46 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-22 8:21 [PATCH v3 0/4] mm: arm64: bring up BATCHED_UNMAP_TLB_FLUSH Yicong Yang
2022-08-22 8:21 ` [PATCH v3 1/4] Revert "Documentation/features: mark BATCHED_UNMAP_TLB_FLUSH doesn't apply to ARM64" Yicong Yang
2022-09-09 4:26 ` Anshuman Khandual
2022-09-09 4:40 ` Barry Song
2022-08-22 8:21 ` [PATCH v3 2/4] mm/tlbbatch: Introduce arch_tlbbatch_should_defer() Yicong Yang
2022-08-24 9:40 ` Kefeng Wang
2022-09-09 4:16 ` Anshuman Khandual
2022-08-22 8:21 ` [PATCH v3 3/4] mm: rmap: Extend tlbbatch APIs to fit new platforms Yicong Yang
2022-08-24 9:43 ` Kefeng Wang
2022-09-09 4:51 ` Anshuman Khandual
2022-09-09 5:25 ` Barry Song
2022-08-22 8:21 ` [PATCH v3 4/4] arm64: support batched/deferred tlb shootdown during page reclamation Yicong Yang
2022-08-24 9:46 ` Kefeng Wang
2022-09-09 5:24 ` Anshuman Khandual
2022-09-09 5:35 ` Barry Song
2022-09-09 6:32 ` Yicong Yang
2022-09-15 6:07 ` Anshuman Khandual
2022-09-15 6:42 ` Barry Song
2022-09-15 14:31 ` Nadav Amit
2022-09-19 2:46 ` Anshuman Khandual
2022-09-19 4:24 ` Anshuman Khandual
2022-09-19 4:53 ` Barry Song
2022-09-19 5:08 ` Barry Song
2022-09-20 3:00 ` Anshuman Khandual
2022-09-20 3:39 ` Barry Song
2022-09-20 8:45 ` Anshuman Khandual [this message]
2022-09-21 1:50 ` Barry Song
2022-09-21 1:51 ` Barry Song
2022-09-21 3:33 ` Anshuman Khandual
2022-09-21 6:53 ` Anshuman Khandual
2022-09-21 7:15 ` Barry Song
2022-09-21 7:17 ` Nadav Amit
2022-09-22 3:15 ` Anshuman Khandual
2022-09-06 8:53 ` [PATCH v3 0/4] mm: arm64: bring up BATCHED_UNMAP_TLB_FLUSH Yicong Yang
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