Igor Mitsyanko <i.mitsya...@samsung.com> writes: > On 07/31/2012 07:43 PM, Peter Maydell wrote: >> On 27 July 2012 20:29, Igor Mitsyanko <i.mitsya...@samsung.com> wrote: >>> Rather that repeatedly call SD_GET_CLASS() in a loop, call it once before >>> a loop starts. >> Anthony claims that SD_GET_CLASS should be cheap enough that we don't >> need to hoist it out of loops like this. Do you have profiling data >> or similar that caused you to write this patch? >> >> -- PMM >> > Well, I've tested it by measuring an execution time of a 4Kb write to SD > card, results showed that arithmetic mean of time for one 4k write was > less by ~300us in sequence with SD_GET_CLASS extracted from the loop.
How many loop iterations that? 300us is a huge amount of time, unless you were looping on every byte, I have a hard time understanding that delta. Regards, Anthony Liguori > Although I ran this test several times, I have little faith in test > methodology and results, it obviously showed significant dispersion > between measured time of distinct 4K writes (200-300% if I recall > correctly). I really have no objection no objection to dropping this patch.
