linux-kernel - Re: [PATCH v4 7/9] iommu/vt-d: Add trace events for domain map/unmap

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Date:   Wed, 12 Jun 2019 10:31:34 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@....de>, ashok.raj@...el.com,
        jacob.jun.pan@...el.com, alan.cox@...el.com, kevin.tian@...el.com,
        mika.westerberg@...ux.intel.com, Ingo Molnar <mingo@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        pengfei.xu@...el.com, Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Jonathan Corbet <corbet@....net>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v4 7/9] iommu/vt-d: Add trace events for domain map/unmap

Hi,

On 6/11/19 12:08 AM, Konrad Rzeszutek Wilk wrote:
> On Mon, Jun 03, 2019 at 09:16:18AM +0800, Lu Baolu wrote:
>> This adds trace support for the Intel IOMMU driver. It
>> also declares some events which could be used to trace
>> the events when an IOVA is being mapped or unmapped in
>> a domain.
> 
> Is that even needed considering SWIOTLB also has tracing events?
> 

Currently there isn't any trace point in swiotlb_tbl_map_single().
If we want to add trace point there, I hope we can distinguish the
bounce page events from other use cases (such as bounce buffer for
direct dma), so that we could calculate how many percents of DMA buffers
used by a specific device driver needs to use bounce page.

Best regards,
Baolu