From: Keith Busch <kbusch@kernel.org>
To: Jonathan Derrick <jonathan.derrick@linux.dev>
Cc: korantwork@gmail.com, 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: Thu, 22 Dec 2022 14:56:16 -0700 [thread overview]
Message-ID: <Y6TSgGdCTvkwPiVg@kbusch-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <3d1834d9-7905-1225-741a-f298dd5b8a8e@linux.dev>
On Thu, Dec 22, 2022 at 02:15:20AM -0700, Jonathan Derrick wrote:
> On 12/22/22 12:26 AM, korantwork@gmail.com wrote:
> >
> > However, the bypass mode could increase the interrupts costs in CPU.
> > We test 12 disks in the 6 CPU,
>
> Well the bypass mode was made to improve performance where you have >4
> drives so this is pretty surprising. With bypass mode disabled, VMD will
> intercept and forward interrupts, increasing costs.
>
> I think Nirmal would want to to understand if there's some other factor
> going on here.
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.
The fio jobs could also probably set their cpus_allowed differently to
get better performance in the bypass mode.
next prev parent reply other threads:[~2022-12-22 21:56 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 [this message]
2022-12-23 8:02 ` Xinghui Li
2022-12-27 22:32 ` Jonathan Derrick
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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