From: Jonathan Derrick <jonathan.derrick@linux.dev>
To: Xinghui Li <korantwork@gmail.com>, Keith Busch <kbusch@kernel.org>
Cc: nirmal.patel@linux.intel.com, lpieralisi@kernel.org,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Xinghui Li <korantli@tencent.com>
Subject: Re: [PATCH] PCI: vmd: Do not disable MSI-X remapping in VMD 28C0 controller
Date: Tue, 27 Dec 2022 16:32:17 -0600 [thread overview]
Message-ID: <d14ac29d-027a-08a7-c5c8-848a6920d4a2@linux.dev> (raw)
In-Reply-To: <CAEm4hYUWf+Fx3FV7vNTc8+O9NSb0iQp75MTC6gra6XapXK=cxw@mail.gmail.com>
On 12/23/2022 2:02 AM, Xinghui Li wrote:
> Keith Busch <kbusch@kernel.org> 于2022年12月23日周五 05:56写道：
>>
>> With 12 drives and only 6 CPUs, the bypass mode is going to get more irq
>> context switching. Sounds like the non-bypass mode is aggregating and
>> spreading interrupts across the cores better, but there's probably some
>> cpu:drive count tipping point where performance favors the other way.
>
> We found that tunning the interrupt aggregation can also bring the
> drive performance back to normal.
>
>> The fio jobs could also probably set their cpus_allowed differently to
>> get better performance in the bypass mode.
>
> We used the cpus_allowed in FIO to fix 12 dirves in 6 different CPU.
>
> By the way, sorry for emailing twice, the last one had the format problem.
The bypass mode should help in the cases where drives irqs (eg nproc) exceed
VMD I/O irqs. VMD I/O irqs for 28c0 should be min(63, nproc). You have
very few cpus for a Skylake system with that many drives, unless you mean you
are explicitly restricting the 12 drives to only 6 cpus. Either way, bypass mode
is effectively VMD-disabled, which points to other issues. Though I have also seen
much smaller interrupt aggregation benefits.
next prev parent reply other threads:[~2022-12-27 22:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-22 7:26 [PATCH] PCI: vmd: Do not disable MSI-X remapping in VMD 28C0 controller korantwork
2022-12-22 9:15 ` Jonathan Derrick
2022-12-22 21:56 ` Keith Busch
2022-12-23 8:02 ` Xinghui Li
2022-12-27 22:32 ` Jonathan Derrick [this message]
2022-12-28 2:19 ` Xinghui Li
2023-01-09 21:00 ` Jonathan Derrick
2023-01-10 12:28 ` Xinghui Li
2023-02-06 12:45 ` Xinghui Li
2023-02-06 18:11 ` Patel, Nirmal
2023-02-06 18:28 ` Keith Busch
2023-02-07 3:18 ` Xinghui Li
2023-02-07 20:32 ` Patel, Nirmal
2023-02-09 12:05 ` Xinghui Li
2023-02-09 23:05 ` Keith Busch
2023-02-09 23:57 ` Patel, Nirmal
2023-02-10 0:47 ` Keith Busch
2022-12-23 7:53 ` Xinghui Li
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