Am 07.03.2014 13:39, schrieb Austin S Hemmelgarn: > On 2014-03-06 08:28, Richard Weinberger wrote: >> On Wed, Mar 5, 2014 at 6:37 AM, Jon Ringle <[email protected]> >> wrote: >>> >>> >>> On Wed, 5 Mar 2014, Greg KH wrote: >>> >>>> On Tue, Mar 04, 2014 at 07:01:49PM -0500, Jon Ringle wrote: >>>>> +config CC_OPTIMIZE_FOR_SPEED + bool "Optimze for speed >>>>> (-O3)" + help + Enabling this option will pass "-O3" >>>>> to gcc + resulting in a larger kernel (but possibly >>>>> faster) >>>> >>>> Are you sure about that? Have you measured it? >>> >>> I do know that there is an improvement performance-wise for my >>> particular use-case. >>> >>> My target is an ARM board being built with gcc-4.8.2. My board >>> has on it a sc16is740 that is used as an RS-485 port. The >>> sc16is740 is on the i2c bus, so when an interrupt comes in to >>> indicate that there is data available to be read, I need to get >>> the data over the i2c bus. I do this on a kthread to do this >>> work. The i2c transactions (using i2c-davinci driver) are also >>> interrupt driven. I was seeing a lot of lost packets when >>> receiving data at only 19200. Adding the -O3 compile option >>> helped in this regard in that I am now rarely seeing packet >>> loss. >> >> Please also see: >> http://www.gossamer-threads.com/lists/linux/kernel/1835761?do=post_view_threaded#1835761 >> >> > Ironically, combining these might achieve a significant performance > improvement over CONFIG_GENERIC_CPU and -O2.
*might* We still need a sane proof. Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
