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From: Jingyi Wang <wangjingyi11@huawei.com>
To: Marc Zyngier <maz@kernel.org>
Cc: <kvm@vger.kernel.org>, <kvmarm@lists.cs.columbia.edu>,
	<linux-arm-kernel@lists.infradead.org>, <will@kernel.org>,
	<catalin.marinas@arm.com>, <james.morse@arm.com>,
	<julien.thierry.kdev@gmail.com>, <suzuki.poulose@arm.com>,
	<wanghaibin.wang@huawei.com>, <yezengruan@huawei.com>,
	<shameerali.kolothum.thodi@huawei.com>, <fanhenglong@huawei.com>,
	<prime.zeng@hisilicon.com>
Subject: Re: [RFC PATCH 0/4] Add support for ARMv8.6 TWED feature
Date: Thu, 26 Nov 2020 10:31:03 +0800	[thread overview]
Message-ID: <b084262b-5563-2d80-3065-cf563d978ea3@huawei.com> (raw)
In-Reply-To: <10463cb9a0ae167a89300185c1de348c@kernel.org>

Hi Marc，

I will consider more circumstances in the later test. Thanks for the
advice.

Thanks,
Jingyi


On 11/24/2020 7:02 PM, Marc Zyngier wrote:
> On 2020-11-13 07:54, Jingyi Wang wrote:
>> Hi all，
>>
>> Sorry for the delay. I have been testing the TWED feature performance
>> lately. We select unixbench as the benchmark for some items of it is
>> lock-intensive(fstime/fsbuffer/fsdisk). We run unixbench on a 4-VCPU
>> VM, and bind every two VCPUs on one PCPU. Fixed TWED value is used and
>> here is the result.
> 
> How representative is this?
> 
> TBH, I only know of two real world configurations: one where
> the vCPUs are pinned to different physical CPUs (and in this
> case your patch has absolutely no effect as long as there is
> no concurrent tasks), and one where there is oversubscription,
> and the scheduler moves things around as it sees fit, depending
> on the load.
> 
> Having two vCPUs pinned per CPU feels like a test that has been
> picked to give the result you wanted. I'd like to see the full
> picture, including the case that matters for current use cases.
> I'm specially interested in the cases where the system is
> oversubscribed, because TWED is definitely going to screw with
> the scheduler latency.
> 
> Thanks,
> 
>          M.

WARNING: multiple messages have this Message-ID (diff)
From: Jingyi Wang <wangjingyi11@huawei.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, catalin.marinas@arm.com,
	fanhenglong@huawei.com, prime.zeng@hisilicon.com,
	will@kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 0/4] Add support for ARMv8.6 TWED feature
Date: Thu, 26 Nov 2020 10:31:03 +0800	[thread overview]
Message-ID: <b084262b-5563-2d80-3065-cf563d978ea3@huawei.com> (raw)
In-Reply-To: <10463cb9a0ae167a89300185c1de348c@kernel.org>

Hi Marc，

I will consider more circumstances in the later test. Thanks for the
advice.

Thanks,
Jingyi


On 11/24/2020 7:02 PM, Marc Zyngier wrote:
> On 2020-11-13 07:54, Jingyi Wang wrote:
>> Hi all，
>>
>> Sorry for the delay. I have been testing the TWED feature performance
>> lately. We select unixbench as the benchmark for some items of it is
>> lock-intensive(fstime/fsbuffer/fsdisk). We run unixbench on a 4-VCPU
>> VM, and bind every two VCPUs on one PCPU. Fixed TWED value is used and
>> here is the result.
> 
> How representative is this?
> 
> TBH, I only know of two real world configurations: one where
> the vCPUs are pinned to different physical CPUs (and in this
> case your patch has absolutely no effect as long as there is
> no concurrent tasks), and one where there is oversubscription,
> and the scheduler moves things around as it sees fit, depending
> on the load.
> 
> Having two vCPUs pinned per CPU feels like a test that has been
> picked to give the result you wanted. I'd like to see the full
> picture, including the case that matters for current use cases.
> I'm specially interested in the cases where the system is
> oversubscribed, because TWED is definitely going to screw with
> the scheduler latency.
> 
> Thanks,
> 
>          M.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Jingyi Wang <wangjingyi11@huawei.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, suzuki.poulose@arm.com,
	catalin.marinas@arm.com, shameerali.kolothum.thodi@huawei.com,
	yezengruan@huawei.com, fanhenglong@huawei.com,
	james.morse@arm.com, julien.thierry.kdev@gmail.com,
	prime.zeng@hisilicon.com, wanghaibin.wang@huawei.com,
	will@kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 0/4] Add support for ARMv8.6 TWED feature
Date: Thu, 26 Nov 2020 10:31:03 +0800	[thread overview]
Message-ID: <b084262b-5563-2d80-3065-cf563d978ea3@huawei.com> (raw)
In-Reply-To: <10463cb9a0ae167a89300185c1de348c@kernel.org>

Hi Marc，

I will consider more circumstances in the later test. Thanks for the
advice.

Thanks,
Jingyi


On 11/24/2020 7:02 PM, Marc Zyngier wrote:
> On 2020-11-13 07:54, Jingyi Wang wrote:
>> Hi all，
>>
>> Sorry for the delay. I have been testing the TWED feature performance
>> lately. We select unixbench as the benchmark for some items of it is
>> lock-intensive(fstime/fsbuffer/fsdisk). We run unixbench on a 4-VCPU
>> VM, and bind every two VCPUs on one PCPU. Fixed TWED value is used and
>> here is the result.
> 
> How representative is this?
> 
> TBH, I only know of two real world configurations: one where
> the vCPUs are pinned to different physical CPUs (and in this
> case your patch has absolutely no effect as long as there is
> no concurrent tasks), and one where there is oversubscription,
> and the scheduler moves things around as it sees fit, depending
> on the load.
> 
> Having two vCPUs pinned per CPU feels like a test that has been
> picked to give the result you wanted. I'd like to see the full
> picture, including the case that matters for current use cases.
> I'm specially interested in the cases where the system is
> oversubscribed, because TWED is definitely going to screw with
> the scheduler latency.
> 
> Thanks,
> 
>          M.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-11-26  2:31 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-29  9:17 [RFC PATCH 0/4] Add support for ARMv8.6 TWED feature Jingyi Wang
2020-09-29  9:17 ` Jingyi Wang
2020-09-29  9:17 ` Jingyi Wang
2020-09-29  9:17 ` [RFC PATCH 1/4] arm64: cpufeature: TWED support detection Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17 ` [RFC PATCH 2/4] KVM: arm64: Make use of TWED feature Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17 ` [RFC PATCH 3/4] KVM: arm64: Use dynamic TWE Delay value Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17 ` [RFC PATCH 4/4] KVM: arm64: Add trace for TWED update Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29  9:17   ` Jingyi Wang
2020-09-29 10:50 ` [RFC PATCH 0/4] Add support for ARMv8.6 TWED feature Marc Zyngier
2020-09-29 10:50   ` Marc Zyngier
2020-09-29 10:50   ` Marc Zyngier
2020-09-30  1:21   ` Jingyi Wang
2020-09-30  1:21     ` Jingyi Wang
2020-09-30  1:21     ` Jingyi Wang
2020-11-13  7:54 ` Jingyi Wang
2020-11-13  7:54   ` Jingyi Wang
2020-11-13  7:54   ` Jingyi Wang
2020-11-24  3:19   ` Jingyi Wang
2020-11-24  3:19     ` Jingyi Wang
2020-11-24  3:19     ` Jingyi Wang
2020-11-24 11:02   ` Marc Zyngier
2020-11-24 11:02     ` Marc Zyngier
2020-11-24 11:02     ` Marc Zyngier
2020-11-26  2:31     ` Jingyi Wang [this message]
2020-11-26  2:31       ` Jingyi Wang
2020-11-26  2:31       ` Jingyi Wang

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