From: Alex G <email@example.com> To: Alex Williamson <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Shyam_Iyer@Dell.com, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: [PATCH] PCI/LINK: Account for BW notification in vector calculation Date: Tue, 23 Apr 2019 11:03:04 -0500 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 4/23/19 10:34 AM, Alex Williamson wrote: > On Tue, 23 Apr 2019 09:33:53 -0500 > Alex G <email@example.com> wrote: > >> On 4/22/19 7:33 PM, Alex Williamson wrote: >>> On Mon, 22 Apr 2019 19:05:57 -0500 >>> Alex G <firstname.lastname@example.org> wrote: >>>> echo 0000:07:00.0:pcie010 | >>>> sudo tee /sys/bus/pci_express/drivers/pcie_bw_notification/unbind >>> >>> That's a bad solution for users, this is meaningless tracking of a >>> device whose driver is actively managing the link bandwidth for power >>> purposes. >> >> 0.5W savings on a 100+W GPU? I agree it's meaningless. > > Evidence? Regardless, I don't have control of the driver that's making > these changes, but the claim seems unfounded and irrelevant. The number of 5mW/Gb/lane doesn't ring a bell?  . Your GPU supports 5Gb/s, so likely using an older, more power hungry process. I suspect it's still within the same order of magnitude. > I'm assigning a device to a VM [snip] > I can see why we might want to be notified of degraded links due to signal issues, > but what I'm reporting is that there are also entirely normal reasons > [snip] we can't seem to tell the difference Unfortunately, there is no way in PCI-Express to distinguish between an expected link bandwidth change and one due to error. If you're using virt-manager to configure the VM, then virt-manager could have a checkbox to disable link bandwidth management messages. I'd rather we avoid kernel-side heuristics (like Lukas suggested). If you're confident that your link will operate as intended, and don't want messages about it, that's your call as a user -- we shouldn't decide this in the kernel. Alex  https://www.synopsys.com/designware-ip/technical-bulletin/reduce-power-consumption.html
next prev parent reply other threads:[~2019-04-23 16:03 UTC|newest] Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-04-22 22:43 Alex Williamson 2019-04-23 0:05 ` Alex G 2019-04-23 0:33 ` Alex Williamson 2019-04-23 14:33 ` Alex G 2019-04-23 15:34 ` Alex Williamson 2019-04-23 15:49 ` Lukas Wunner 2019-04-23 16:03 ` Alex G [this message] 2019-04-23 16:22 ` Alex Williamson 2019-04-23 16:27 ` Alex G 2019-04-23 16:37 ` Alex Williamson 2019-04-23 17:10 ` Bjorn Helgaas 2019-04-23 17:53 ` Alex G 2019-04-23 18:38 ` Alex Williamson 2019-04-23 17:59 ` Alex G 2019-05-01 20:30 ` Bjorn Helgaas
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