From: Matthew Wilcox <willy@infradead.org>
To: Tony Battersby <tonyb@cybernetics.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Sathya Prakash <sathya.prakash@broadcom.com>,
Chaitra P B <chaitra.basappa@broadcom.com>,
Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>,
iommu@lists.linux-foundation.org, linux-mm@kvack.org,
linux-scsi <linux-scsi@vger.kernel.org>,
MPT-FusionLinux.pdl@broadcom.com
Subject: Re: [PATCH 2/3] dmapool: improve scalability of dma_pool_free
Date: Thu, 26 Jul 2018 12:42:09 -0700 [thread overview]
Message-ID: <20180726194209.GB12992@bombadil.infradead.org> (raw)
In-Reply-To: <1288e597-a67a-25b3-b7c6-db883ca67a25@cybernetics.com>
On Thu, Jul 26, 2018 at 02:54:56PM -0400, Tony Battersby wrote:
> dma_pool_free() scales poorly when the pool contains many pages because
> pool_find_page() does a linear scan of all allocated pages. Improve its
> scalability by replacing the linear scan with a red-black tree lookup.
> In big O notation, this improves the algorithm from O(n^2) to O(n * log n).
This is a lot of code to get us to O(n * log(n)) when we can use less
code to go to O(n). dma_pool_free() is passed the virtual address.
We can go from virtual address to struct page with virt_to_page().
In struct page, we have 5 words available (20/40 bytes), and it's trivial
to use one of them to point to the struct dma_page.
next prev parent reply other threads:[~2018-07-26 19:42 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-26 18:54 [PATCH 2/3] dmapool: improve scalability of dma_pool_free Tony Battersby
2018-07-26 19:42 ` Matthew Wilcox [this message]
2018-07-26 20:06 ` Tony Battersby
2018-07-27 0:07 ` Matthew Wilcox
2018-07-27 13:23 ` Tony Battersby
2018-07-27 15:23 ` Matthew Wilcox
2018-07-27 19:38 ` Tony Battersby
2018-07-27 21:27 ` Tony Battersby
2018-07-27 21:35 ` Andy Shevchenko
2018-07-27 22:07 ` Tony Battersby
2018-07-30 14:05 ` Tony Battersby
2018-07-26 19:45 ` Andy Shevchenko
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