From: Xinghui Li <korantwork@gmail.com>
To: Jonathan Derrick <jonathan.derrick@linux.dev>
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: Fri, 23 Dec 2022 15:53:12 +0800 [thread overview]
Message-ID: <CAEm4hYUeigWxcDVGpg05P-5Qkh=6bArmtPqVqxR6Yw4wod3WBA@mail.gmail.com> (raw)
In-Reply-To: <3d1834d9-7905-1225-741a-f298dd5b8a8e@linux.dev>
Jonathan Derrick <jonathan.derrick@linux.dev> 于2022年12月22日周四 17:15写道:
>
>
>
> On 12/22/22 12:26 AM, korantwork@gmail.com wrote:
> > From: Xinghui Li <korantli@tencent.com>
> >
> > Commit ee81ee84f873("PCI: vmd: Disable MSI-X remapping when possible")
> > disable the vmd MSI-X remapping for optimizing pci performance.However,
> > this feature severely negatively optimized performance in multi-disk
> > situations.
> >
> > In FIO 4K random test, we test 1 disk in the 1 CPU
> >
> > when disable MSI-X remapping:
> > read: IOPS=1183k, BW=4622MiB/s (4847MB/s)(1354GiB/300001msec)
> > READ: bw=4622MiB/s (4847MB/s), 4622MiB/s-4622MiB/s (4847MB/s-4847MB/s),
> > io=1354GiB (1454GB), run=300001-300001msec
> >
> > When not disable MSI-X remapping:
> > read: IOPS=1171k, BW=4572MiB/s (4795MB/s)(1340GiB/300001msec)
> > READ: bw=4572MiB/s (4795MB/s), 4572MiB/s-4572MiB/s (4795MB/s-4795MB/s),
> > io=1340GiB (1438GB), run=300001-300001msec
> >
> > 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.
We also find the more drives we tested, the more severe the
performance degradation.
When we tested 8 drives in 6 CPU, there is about 30% drop.
> I think Nirmal would want to to understand if there's some other factor
> going on here.
I also agree with this. The tested server is None io-scheduler.
We tested the same server. Tested drives are Samsung Gen-4 nvme.
Is there anything else you worried effecting test results?
prev parent reply other threads:[~2022-12-23 7:53 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
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 [this message]
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