linux-kernel - Re: [PATCH v2] iommu/iova: silence warnings under memory pressure

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Message-ID: <7fd08d481a372ea0b600f95c12166ab54ed5e267.camel@perches.com>
Date:   Thu, 21 Nov 2019 20:37:48 -0800
From:   Joe Perches <joe@...ches.com>
To:     Qian Cai <cai@....pw>, jroedel@...e.de
Cc:     baolu.lu@...ux.intel.com, dwmw2@...radead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iommu/iova: silence warnings under memory pressure

On Thu, 2019-11-21 at 21:55 -0500, Qian Cai wrote:
> When running heavy memory pressure workloads, this 5+ old system is
> throwing endless warnings below because disk IO is too slow to recover
> from swapping. Since the volume from alloc_iova_fast() could be large,
> once it calls printk(), it will trigger disk IO (writing to the log
> files) and pending softirqs which could cause an infinite loop and make
> no progress for days by the ongoimng memory reclaim. This is the counter
> part for Intel where the AMD part has already been merged. See the
> commit 3d708895325b ("iommu/amd: Silence warnings under memory
> pressure"). Since the allocation failure will be reported in
> intel_alloc_iova(), so just call printk_ratelimted() there and silence
> the one in alloc_iova_mem() to avoid the expensive warn_alloc().
[]
> v2: use dev_err_ratelimited() and improve the commit messages.
[]
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
[]
> @@ -3401,7 +3401,8 @@ static unsigned long intel_alloc_iova(struct device *dev,
>  	iova_pfn = alloc_iova_fast(&domain->iovad, nrpages,
>  				   IOVA_PFN(dma_mask), true);
>  	if (unlikely(!iova_pfn)) {
> -		dev_err(dev, "Allocating %ld-page iova failed", nrpages);
> +		dev_err_ratelimited(dev, "Allocating %ld-page iova failed",
> +				    nrpages);

Trivia:

This should really have a \n termination on the format string

		dev_err_ratelimited(dev, "Allocating %ld-page iova failed\n",