From mboxrd@z Thu Jan 1 00:00:00 1970 From: Afzal Mohammed Date: Mon, 24 Aug 2015 13:53:48 +0000 Subject: Re: [RFC] fbdev/riva:change to use generice function to implement reverse_order() Message-Id: <20150824134148.GA3394@afzalpc> List-Id: References: <55D5B3A9.6040901@ti.com> <867D66CD-9A3B-4536-B537-8C065C85E497@gmail.com> <55D6C812.6080400@ti.com> <4DCC50F3-9B6D-4A3A-9693-E7A7196564A8@gmail.com> <55D6DAE5.20304@ti.com> <20150822075310.GA2337@afzalpc> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: yalin wang Cc: Tomi Valkeinen , adaplas@gmail.com, plagnioj@jcrosoft.com, linux-fbdev@vger.kernel.org, open list Hi, On Mon, Aug 24, 2015 at 04:31:13PM +0800, yalin wang wrote: > > i only submit the bit reverse patch for arm / arm64 arch, yes, saw later git blaming it on you :) > > Not for this case, but once measured on ARM, iirc, a 32-bit asm bit > > reversal as compared to doing it in C was taking 1 cycle as opposed to > > ~225 cycles!, of course writing optimized C could have made it fare > > better, but still would reach no-way near asm bit reversal. The above measurement was done not in Linux, rather on a baremetal code, but seeing the efficient Kernel C implementation, realized that the gain would not be that much, it would be good to know if there are measurements for Kernel bitreversal in C & asm (on supported arch) Regards afzal