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Message-Id: <20130409132202.a73a059ab2b57d47d6f1652b@linux-foundation.org> Date: Tue, 9 Apr 2013 13:22:02 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: "Chanho Min" <chanho.min@....com> Cc: "'Nadia Yvette Chambers'" <nyc@...omorphy.com>, "'Jiri Kosina'" <jkosina@...e.cz>, "'Guennadi Liakhovetski'" <lg@...x.de>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2] bitmap: speedup in bitmap_find_free_region when order is 0 On Tue, 9 Apr 2013 15:34:44 +0900 "Chanho Min" <chanho.min@....com> wrote: > >It seems excessively complicated to me. Why not change > >bitmap_find_free_region() to skip the leading all-ones words and when > >it finds a not-all-ones word, adjust `pos' then fall into the existing > >bit-at-a-time search? > > Do we need the additional 'if' inside the for loop for implementing it? It was just a concept - there are various ways of optimizing a real implementation. Move the code into userspace then run some microbenchmarks. > I thought the separation of the routine for order=0 is the way to avoid > the impact on the existing codes and its performance. The existing code doesn't have any performance ;) It's so darn slow that even a minor effort here will yield large (ie order-of-magnitude) performance improvements. -- 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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