From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Tue, 13 Jan 2015 17:34:05 +0100 Subject: CFT: move outer_cache_sync() out of line In-Reply-To: <20150112163648.GL12302@n2100.arm.linux.org.uk> References: <20150112163648.GL12302@n2100.arm.linux.org.uk> Message-ID: <4576899.a2tdJxHBKo@wuerfel> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Monday 12 January 2015 16:36:48 Russell King - ARM Linux wrote: > Theoretically, this should help overall system performance, since the > branch predictor should be able to predict this better, but it's entirely > possible that trying to benchmark a single workload won't be measurably > different. > > In terms of kernel size figures, this change alone saves almost 17K of > 10MB of kernel text on my iMX6 kernels - which is bordering on > insignificant since that's not quite a 0.2% saving. > > So... right now I can't justify this change, but I'm hoping some can come > up with some figures which shows that it benefits their workload without > causing a performance regression for others. >>From the theory, I think it can only help to do this. I would guess that the time spent inside of the cache_sync function dwarfs both the extra unconditional branch you introduce and the possible misprediction, so 17K in space savings sounds like more than enough justification to just do it. Acked-by: Arnd Bergmann