From: Will Deacon <will@kernel.org>
To: Zhenyu Ye <yezhenyu2@huawei.com>
Cc: catalin.marinas@arm.com, maz@kernel.org, suzuki.poulose@arm.com,
mark.rutland@arm.com, tangnianyao@huawei.com,
xiexiangyou@huawei.com, linux-kernel@vger.kernel.org,
arm@kernel.org
Subject: Re: [RFC PATCH v2] arm64: cpufeatures: add support for tlbi range instructions
Date: Mon, 11 Nov 2019 13:27:17 +0000 [thread overview]
Message-ID: <20191111132716.GA9394@willie-the-truck> (raw)
In-Reply-To: <5DC960EB.9050503@huawei.com>
On Mon, Nov 11, 2019 at 09:23:55PM +0800, Zhenyu Ye wrote:
> ARMv8.4-TLBI provides TLBI invalidation instruction that apply to a
> range of input addresses. This patch adds support for this feature.
> This is the second version of the patch.
>
> I traced the __flush_tlb_range() for a minute and get some statistical
> data as below:
>
> PAGENUM COUNT
> 1 34944
> 2 5683
> 3 1343
> 4 7857
> 5 838
> 9 339
> 16 933
> 19 427
> 20 5821
> 23 279
> 41 338
> 141 279
> 512 428
> 1668 120
> 2038 100
>
> Those data are based on kernel-5.4.0, where PAGENUM = end - start, COUNT
> shows number of calls to the __flush_tlb_range() in a minute. There only
> shows the data which COUNT >= 100. The kernel is started normally, and
> transparent hugepage is opened. As we can see, though most user TLBI
> ranges were 1 pages long, the num of long-range can not be ignored.
>
> The new feature of TLB range can improve lots of performance compared to
> the current implementation. As an example, flush 512 ranges needs only 1
> instruction as opposed to 512 instructions using current implementation.
>
> And for a new hardware feature, support is better than not.
>
> Signed-off-by: Zhenyu Ye <yezhenyu2@huawei.com>
> ---
> ChangeLog v1 -> v2:
> - Change the main implementation of this feature.
> - Add some comments.
How does this address my concerns here:
https://lore.kernel.org/linux-arm-kernel/20191031131649.GB27196@willie-the-truck/
?
Will
next prev parent reply other threads:[~2019-11-11 13:27 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-11 13:23 [RFC PATCH v2] arm64: cpufeatures: add support for tlbi range instructions Zhenyu Ye
2019-11-11 13:27 ` Will Deacon [this message]
2019-11-11 13:47 ` Zhenyu Ye
2019-11-11 14:04 ` Marc Zyngier
2019-11-11 14:23 ` Zhenyu Ye
2019-11-19 1:13 ` Hanjun Guo
2019-11-19 10:03 ` Marc Zyngier
2019-11-20 1:29 ` Hanjun Guo
2019-11-20 8:47 ` Will Deacon
2019-11-11 16:32 ` Olof Johansson
2019-11-12 2:19 ` Zhenyu Ye
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