Re: [PATCH v2] lib/scatterlist: add simple page iterator

From: Tejun Heo
Date: Tue Feb 12 2013 - 12:13:16 EST


On Tue, Feb 12, 2013 at 07:07:20PM +0200, Imre Deak wrote:
> It's the one implemented by sg_miter_{start,stop} in scatterlist.c. It
> also iterates through a scatterlist a page at a time, but it also kmaps
> these pages. Since in our use case we don't need to map the pages we
> needed a solution without this overhead.

I'm not against having non-mapping iterator but please consider that
kmaps are no-ops on many configurations. It matters only for archs w/
high memory.

> where each entry on the sglist contained 16 consecutive pages. This
> takes ~10% more time for the uninlined version to run. This is a rather
> artificial test and I couldn't come up with something more real-life
> using only the i915 driver's ioctl interface that would show a
> significant change in speed.
> So at least for now I'm ok with just uninlining all the helpers.

Can we reimplement mapping iters using the new ones?


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