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Message-Id: <200610111125.10902.arnd@arndb.de> Date: Wed, 11 Oct 2006 11:25:09 +0200 From: Arnd Bergmann <arnd@...db.de> To: Geoff Levand <geoffrey.levand@...sony.com> Cc: jschopp <jschopp@...tin.ibm.com>, Linas Vepstas <linas@...tin.ibm.com>, akpm@...l.org, jeff@...zik.org, netdev@...r.kernel.org, James K Lewis <jklewis@...ibm.com>, linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org Subject: Re: [PATCH 21/21]: powerpc/cell spidernet DMA coalescing On Wednesday 11 October 2006 03:46, Geoff Levand wrote: > > > > The others look good, but this one complicates the code and doesn't have any benefit. 20 > > for 21 isn't bad. > > Is the motivation for this change to improve performance by reducing the overhead > of the mapping calls? If so, there may be some benefit for some systems. Could > you please elaborate? > >From what I understand, this patch drastically reduces the number of I/O PTEs that are needed in the iommu. With the current static IOMMU mapping, it should only make a difference during initialization, but any platform that uses a dynamic mapping of iommu entries will benefit a lot from it, because: - the card can do better prefetching of consecutive memory - there are more I/O ptes available for other drivers. Arnd <>< - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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