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Message-ID: <1304357805.30823.18.camel@nimitz> Date: Mon, 02 May 2011 10:36:45 -0700 From: Dave Hansen <dave@...ux.vnet.ibm.com> To: Eric Paris <eparis@...hat.com> Cc: linux-kernel@...r.kernel.org, Jesse Gross <jesse@...ira.com>, David Rientjes <rientjes@...gle.com>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH] flex_array: avoid divisions when accessing elements On Mon, 2011-05-02 at 13:26 -0400, Eric Paris wrote: > On most architectures division is an expensive operation and accessing an > element currently requires four of them. This performance penalty > effectively precludes flex arrays from being used on any kind of fast > path. However, two of these divisions can be handled at creation time and > the others can be replaced by a reciprocal divide, completely avoiding > real divisions on access. > > Signed-off-by: Jesse Gross <jesse@...ira.com> > Cc: David Rientjes <rientjes@...gle.com> > Cc: Eric Paris <eparis@...hat.com> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org> > [rebase on top of changes to support 0 len elements: eparis] > [initialize part_nr when array fits entirely in base: eparis] > Signed-off-by: Eric Paris <eparis@...hat.com> This seems sane to me, especially in the element access case. Acked-by: Dave Hansen <dave@...ux.vnet.ibm.com> -- Dave -- 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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