From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BF7B51FF5F9; Wed, 9 Jul 2025 20:26:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752092784; cv=none; b=jY7WG7qMdFJalBeOnqduP6bGJVqx14FzsICrCgLsR+TsoW5pEQfIBCJPT7bY8hq1Ad3yBN1xI5s7iYucvu0sSG02tfakk3mKwyUW3SnuSr6U0iEiaQzoJz7coBUEI8v6xUrRcv0z5cq4QRMz7gMxiXLdAWeUB4SgGeYa4haLt9w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752092784; c=relaxed/simple; bh=bQNwEAhweMYICewYFBrSb4iT3iREmwhVhLODYftXieE=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=rq+2qKTGPeQmfqfUTMFuBeafrJccTdKNlB2Y85GsOXDyzu7dSG55auSQClo7vyS0w6oMuZLbc8p882oFv3xAmSJxJr8cdZKzau4Z3eJ2nDp5l92lCdM1CUmt2xWbZ8TW3IgXa/sfb1Ov7d0U3lOiHCRqxsOH1QbAUSwxnShswiU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PNSrPjem; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PNSrPjem" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32D34C4CEEF; Wed, 9 Jul 2025 20:26:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752092784; bh=bQNwEAhweMYICewYFBrSb4iT3iREmwhVhLODYftXieE=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=PNSrPjemNmqhvpwmzgy6nx4B4VTCC+toNXpRJUmDZsaKgg2BzuxwggCCth6MoSda0 RCK23XDaqRvE503RV/W3S/SiTKQL7zM4zjjrO4YnRHTjihJyMcXCltwQingacv3XmB +lRc+HJgdL/iR8oXLajeNIG4y7WDGkCHWZSWpMkciX8CexrewxfyzzZUPKNVbp6BIE 11gk2rd238anzodUaiqvpSUsMzYlviyG+alCRHnYm5v1lAC7nSKQNIuxRy4xWKB1lu jhi9t0Ifk+wXGSrm1kfMWYBXjNjdZARiPjzs4qUCmAcL2U86hclGWLXGGW+Ki45oyd AxW7PgRNzU82g== Date: Wed, 9 Jul 2025 15:26:22 -0500 From: Bjorn Helgaas To: Ammar Qadri Cc: Manivannan Sadhasivam , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI: Reduce verbosity of device enable messages Message-ID: <20250709202622.GA2207975@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Jul 09, 2025 at 11:25:54AM -0700, Ammar Qadri wrote: > This is the only message I can see being consistently printed as a > result of the open/close of the devices. > > I am not opposed to carrying this out of tree at all, but for the sake > of exhausting options people would be comfortable with, would you > be okay with moving this to dev_dbg, or would you have the same > hesitations, Mani (et al)? Or is there some alternative flag-controlled > behavior you'd recommend? pci_dbg() (as you proposed) is just syntactic sugar for dev_dbg(), so they're functionally the same. Personally I think "enabling device (0000 -> 0002)" is probably not interesting enough to be an 'info' message. Every driver is going to call pci_enable_device() (unless it only uses config space). If it wants to emit a message in its .probe() function it can, and it can include more useful information than whether we're setting the Memory or I/O decoding enable bits. We already have a similar "enabling bus mastering" message in __pci_set_master() that is already pci_dbg(). So I propose: - Demoting it to pci_dbg() - Decoding the bits, e.g., "enabling MEM decoding" - Adding hints about how to enable pci_dbg() messages to Documentation/admin-guide/kernel-parameters.txt > On Fri, Jun 13, 2025 at 3:09 PM Bjorn Helgaas wrote: > > > > On Fri, Jun 13, 2025 at 02:40:40PM -0700, Ammar Qadri wrote: > > > Hi Mani, > > > > > > The issue we are experiencing is not caused from > > > removing/reattaching the device driver, so the other messages have > > > not been problematic. > > > > > > The vfio-pci driver is attached to each VF once. Clients in our > > > system call open and close on the vfio-pci driver, respectively, at > > > the start and end of their use, with fairly short-term tenancy, > > > which ends up triggering these enable messages. This message is > > > proving challenging not only because they are not particularly > > > useful, but because they are causing log files to rotate once every > > > 30 minutes or so, and we lose a lot of other more valuable logging > > > as a consequence. I'm open to other solutions, but in my opinion > > > this preserves the message, without over-engineering and introducing > > > throttling or other behaviour. > > > > Are there any other messages associated with the open/close? I assume > > probably not, or you would want to demote those as well. > > > > I did happen to find some value in this particular message just the > > other day because it showed that a config read was successful after > > previous ones had failed. > > > > But I agree in general that it's fairly low value and at least the > > uninterpreted "%04x -> %04x" part is not really user-friendly. > > > > If people think there's enough value in retaining it at KERN_INFO, I > > suppose there's always the option of carrying an out-of-tree patch to > > demote it? > > > > > On Thu, Jun 12, 2025 at 11:12 PM Manivannan Sadhasivam wrote: > > > > > > > > On Wed, May 07, 2025 at 11:29:19PM +0000, Ammar Qadri wrote: > > > > > Excessive logging of PCIe device enable operations can create significant > > > > > noise in system logs, especially in environments with a high number of > > > > > such devices, especially VFs. > > > > > > > > > > High-rate logging can cause log files to rotate too quickly, losing > > > > > valuable information from other system components.This commit addresses > > > > > this issue by downgrading the logging level of "enabling device" messages > > > > > from `info` to `dbg`. > > > > > > > > > > > > > While I generally prefer reduced verbosity of the device drivers, demoting an > > > > existing log to debug might surprise users. Especially in this case, the message > > > > is widely used to identify the enablement of a PCI device. So I don't think it > > > > is a good idea to demote it to a debug log. > > > > > > > > But I'm surprised that this single message is creating much overhead in the > > > > logging. I understand that you might have 100s of VFs in cloud environments, but > > > > when a VF is added, a bunch of other messages would also get printed (resource, > > > > IRQ, device driver etc...). Or you considered that this message is not that > > > > important compared to the rest? > > > > > > > > - Mani > > > > > > > > > Signed-off-by: Ammar Qadri > > > > > --- > > > > > drivers/pci/setup-res.c | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c > > > > > index c6657cdd06f67..be669ff6ca240 100644 > > > > > --- a/drivers/pci/setup-res.c > > > > > +++ b/drivers/pci/setup-res.c > > > > > @@ -516,7 +516,7 @@ int pci_enable_resources(struct pci_dev *dev, int mask) > > > > > } > > > > > > > > > > if (cmd != old_cmd) { > > > > > - pci_info(dev, "enabling device (%04x -> %04x)\n", old_cmd, cmd); > > > > > + pci_dbg(dev, "enabling device (%04x -> %04x)\n", old_cmd, cmd); > > > > > pci_write_config_word(dev, PCI_COMMAND, cmd); > > > > > } > > > > > return 0; > > > > > -- > > > > > 2.49.0.987.g0cc8ee98dc-goog > > > > > > > > > > > > > -- > > > > மணிவண்ணன் சதாசிவம்