linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bjorn Helgaas <helgaas@kernel.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: "Alex G." <mr.nuke.me@gmail.com>,
	linux-pci@vger.kernel.org, "Bolen,
	Austin" <austin_bolen@dell.com>, Keith Busch <kbusch@kernel.org>
Subject: Re: spammy dmesg about fluctuating pcie bandwidth on 5.9
Date: Mon, 12 Oct 2020 17:03:25 -0500	[thread overview]
Message-ID: <20201012220325.GA3752081@bjorn-Precision-5520> (raw)
In-Reply-To: <CAHmME9qa4NQCj8w-Apd2TnbtMjbox0jA6T347Bf_wEkJrzSz0g@mail.gmail.com>

On Fri, Oct 09, 2020 at 05:17:53PM +0200, Jason A. Donenfeld wrote:
> Interestingly, some of the time that I run that lspci command, the
> dmesg line is provoked. That sort of makes sense, since lspci is
> communicating over the bus to gather all that info. I ran the command
> a few times and stored the output, if you want to look at their diffs.
> See attached.

The dmesg logs from your initial report:

  pcieport 0000:04:00.0: 31.504 Gb/s available PCIe bandwidth, limited by 8.0 GT/s PCIe x4 link at 0000:00:1b.4 (capable of 1984.941 Gb/s with 32.0 GT/s PCIe x63 link)

are almost certainly seeing ~0 responses to config reads of 04:00.0.
That would happen if 04:00.0 were powered off or if the bridge leading
to it (00:1b.4) were in Downstream Port Containment mode.  00:1b.4
does support DPC, but none of the lspci logs you attached show DPC
being triggered.  If it were, you should see some indication in dmesg
as well, e.g., the "containment event, status:%#06x source:%#06x\n"
message from dpc_process_error().

If you can collect the complete dmesg log, especially after you get
the bandwidth notification spam, it might have a clue.

Just to re-confirm: this happens with v5.8 but not with v5.9?  (v5.9
had not been released at your initial report, so I assume you meant
v5.9-rc8 or something?)

If you can bisect, that would be the easiest way to identify the
problem.

Bjorn

       reply	other threads:[~2020-10-12 22:03 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAHmME9qa4NQCj8w-Apd2TnbtMjbox0jA6T347Bf_wEkJrzSz0g@mail.gmail.com>
2020-10-12 22:03 ` Bjorn Helgaas [this message]
2020-10-14 10:31   ` spammy dmesg about fluctuating pcie bandwidth on 5.9 Jason A. Donenfeld
2020-10-07 16:09 Jason A. Donenfeld
2020-10-07 16:46 ` Keith Busch
2020-10-07 17:02 ` Bjorn Helgaas
2020-10-09 14:32   ` Alex G.
2020-10-09 15:05     ` Bjorn Helgaas

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201012220325.GA3752081@bjorn-Precision-5520 \
    --to=helgaas@kernel.org \
    --cc=Jason@zx2c4.com \
    --cc=austin_bolen@dell.com \
    --cc=kbusch@kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=mr.nuke.me@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).