From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave.martin@linaro.org (Dave Martin) Date: Thu, 7 Jul 2011 16:27:40 +0100 Subject: ARM cortex A9 performance issue In-Reply-To: References: Message-ID: <20110707152740.GG2486@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 07, 2011 at 02:48:05PM +0530, rd bairva wrote: > Hi, > > We are trying to benchmark ARM cortex A9 dual core behavior with > respect to single core > performance and also measuring it with respect to x86 dual core/single core. > Please find attached with the mail is c app which we are using for benchmarking. > > Simple overview of C application: > - It creates a shared memory area using shm_open(). > in this shm area, it declares 2 Process shared pthread mutex, lets say L1, L2. > - then it forks to create a server_task and client task. > - server_task takes L1 lock, touches a shm area, unlock L2, in a loop. > - client_task takes L2 lock, touches a shm area, unlock L1, in a loop. > - This loop runs for N number of times that we measure. The behaviour of pthread_mutex_unlock is unspecified if an attempt is made to ulock a mutex from a thread which doesn't currently own that mutex. You probably need to re-code your test to avoid this incorrect use of the ABI before an interpretation can be placed on the results. See pthread_mutexattr_init(3) for details. Some people have been reported issues related to process shared mutexes on ARM recently: https://bugs.launchpad.net/ubuntu/+source/apr/+bug/604753 I'm not sure of the current status of that though, and I don't know whether it would affect your test or not. Cheers ---Dave > > Here are the results for N/sec for different CPUs. > > Platform Up cores req/sec cpuload > Cortexa9 2 ~44000 > 100% > Cortexa9 1 ~18000 > 100% > X86 2 ~64000 > 35% > X86 1 ~458886 > 100% (1 cpu down by sysfs) > > we are not able to understand the results. > - why for coretx A9 both dual/single core we are getting 100% cpu usage. > - why in case of x86, N/sec is very high for single core than dual core. > - why single core N/s is 1/3 in case of CortexA9. > > Thanks, > Ramdayal > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel