From: Christoph Hellwig <hch@infradead.org>
To: Nicolin Chen <nicoleotsuka@gmail.com>
Cc: joro@8bytes.org, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist
Date: Sun, 4 Nov 2018 07:50:01 -0800 [thread overview]
Message-ID: <20181104155001.GA25794@infradead.org> (raw)
In-Reply-To: <20181101213500.21800-1-nicoleotsuka@gmail.com>
On Thu, Nov 01, 2018 at 02:35:00PM -0700, Nicolin Chen wrote:
> The __GFP_ZERO will be passed down to the generic page allocation
> routine which zeros everything page by page. This is safe to be a
> generic way but not efficient for iommu allocation that organizes
> contiguous pages using scatterlist.
>
> So this changes drops __GFP_ZERO from the flag, and adds a manual
> memset after page/sg allocations, using the length of scatterlist.
>
> My test result of a 2.5MB size allocation shows iommu_dma_alloc()
> takes 46% less time, reduced from averagely 925 usec to 500 usec.
And in what case does dma_alloc_* performance even matter?
next prev parent reply other threads:[~2018-11-04 15:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 21:35 [PATCH] iommu/dma: Zero pages manually in a length of scatterlist Nicolin Chen
2018-11-02 16:54 ` Robin Murphy
2018-11-02 23:36 ` Nicolin Chen
2018-11-05 14:58 ` Christoph Hellwig
2018-11-06 14:39 ` Robin Murphy
2018-11-09 7:45 ` Christoph Hellwig
2018-11-06 18:27 ` Robin Murphy
2018-11-07 0:11 ` Nicolin Chen
2018-11-04 15:50 ` Christoph Hellwig [this message]
2018-11-06 23:46 ` Nicolin Chen
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