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Date: Mon, 6 Feb 2023 20:45:57 +0800
From: Xinghui Li <korantwork@...il.com>
To: Jonathan Derrick <jonathan.derrick@...ux.dev>
Cc: Keith Busch <kbusch@...nel.org>, nirmal.patel@...ux.intel.com,
lpieralisi@...nel.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, Xinghui Li <korantli@...cent.com>
Subject: Re: [PATCH] PCI: vmd: Do not disable MSI-X remapping in VMD 28C0 controller
Friendly ping~
Xinghui Li <korantwork@...il.com> 于2023年1月10日周二 20:28写道：
>
> Jonathan Derrick <jonathan.derrick@...ux.dev> 于2023年1月10日周二 05:00写道：
> >
> > As the bypass mode seems to affect performance greatly depending on the specific configuration,
> > it may make sense to use a moduleparam to control it
> >
> We found that each pcie port can mount four drives. If we only test 2
> or 1 dirve of one pcie port,
> the performance of the drive performance will be normal. Also, we
> observed the interruptions in different modes.
> bypass:
> .....
> 2022-12-28-11-39-14: 1224 181665 IR-PCI-MSI 201850948-edge nvme0q68
> 2022-12-28-11-39-14: 1179 180115 IR-PCI-MSI 201850945-edge nvme0q65
> 2022-12-28-11-39-14: RES 26743 Rescheduling interrupts
> 2022-12-28-11-39-17: irqtop - IRQ : 3029, TOTAL : 2100315228, CPU :
> 192, ACTIVE CPU : 192
> disable:
> ......
> 2022-12-28-12-05-56: 1714 169797 IR-PCI-MSI 14155850-edge nvme1q74
> 2022-12-28-12-05-56: 1701 168753 IR-PCI-MSI 14155849-edge nvme1q73
> 2022-12-28-12-05-56: LOC 163697 Local timer interrupts
> 2022-12-28-12-05-56: TLB 5465 TLB shootdowns
> 2022-12-28-12-06-00: irqtop - IRQ : 3029, TOTAL : 2179022106, CPU :
> 192, ACTIVE CPU : 192
> remapping:
> 022-12-28-11-25-38: 283 325568 IR-PCI-MSI 24651790-edge vmd3
> 2022-12-28-11-25-38: 140 267899 IR-PCI-MSI 13117447-edge vmd1
> 2022-12-28-11-25-38: 183 265978 IR-PCI-MSI 13117490-edge vmd1
> ......
> 2022-12-28-11-25-42: irqtop - IRQ : 2109, TOTAL : 2377172002, CPU :
> 192, ACTIVE CPU : 192
>
> From the result it is not difficult to find, in remapping mode the
> interruptions come from vmd.
> While in other modes, interrupts come from nvme devices. Besides, we
> found the port mounting
> 4 dirves total interruptions is much fewer than the port mounting 2 or 1 drive.
> NVME 8 and 9 mount in one port, other port mount 4 dirves.
>
> 2022-12-28-11-39-14: 2582 494635 IR-PCI-MSI 470810698-edge nvme9q74
> 2022-12-28-11-39-14: 2579 489972 IR-PCI-MSI 470810697-edge nvme9q73
> 2022-12-28-11-39-14: 2573 480024 IR-PCI-MSI 470810695-edge nvme9q71
> 2022-12-28-11-39-14: 2544 312967 IR-PCI-MSI 470286401-edge nvme8q65
> 2022-12-28-11-39-14: 2556 312229 IR-PCI-MSI 470286405-edge nvme8q69
> 2022-12-28-11-39-14: 2547 310013 IR-PCI-MSI 470286402-edge nvme8q66
> 2022-12-28-11-39-14: 2550 308993 IR-PCI-MSI 470286403-edge nvme8q67
> 2022-12-28-11-39-14: 2559 308794 IR-PCI-MSI 470286406-edge nvme8q70
> ......
> 2022-12-28-11-39-14: 1296 185773 IR-PCI-MSI 202375243-edge nvme1q75
> 2022-12-28-11-39-14: 1209 185646 IR-PCI-MSI 201850947-edge nvme0q67
> 2022-12-28-11-39-14: 1831 184151 IR-PCI-MSI 203423828-edge nvme3q84
> 2022-12-28-11-39-14: 1254 182313 IR-PCI-MSI 201850950-edge nvme0q70
> 2022-12-28-11-39-14: 1224 181665 IR-PCI-MSI 201850948-edge nvme0q68
> 2022-12-28-11-39-14: 1179 180115 IR-PCI-MSI 201850945-edge nvme0q65
> > I'd vote for it being in VMD mode (non-bypass) by default.
> I speculate that the vmd controller equalizes the interrupt load and
> acts like a buffer,
> which improves the performance of nvme. I am not sure about my
> analysis. So, I'd like
> to discuss it with the community.
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