Hi, I am observing some degradation in context switch performance (reported by sched benchmark of perf), after including the change to keep thread_info in sp_el0: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6cdf9c7ca687e01840d0215437620a20263012fc However, if I use D0 to store the same information, I see that performance improves. For example, I am getting following numbers for the above mentioned scenarios: Thread info obtained from stack: /data/local # ./perf bench sched messaging -g 5 -l 500 # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 5 groups == 200 processes run Total time: 2.911 [sec] Thread info obtained from sp_el0: /data/local # ./perf bench sched messaging -g 5 -l 500 # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 5 groups == 200 processes run Total time: 3.590 [sec] Thread info obtained from D0: /data/local # ./perf bench sched messaging -g 5 -l 500 # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 5 groups == 200 processes run Total time: 3.103 [sec] So keeping thread_info in sp_el0 is resulting in degradation of around 23% , while keeping the same in D0 is resulting in degradation of about 6-7%. Of course so far my test cases are not involving cases where D0 might get changed in kernel space itself e.g. snippets under kernel_neon_begin/end and taking care of those cases will have further overhead. But right now I just wanted to have a feedback regarding, what are the possible complications I may face if I try to keep thread_info in D0 and whether such a solution will be feasible or not. Moreover is there any other alternative way to get rid of this performance degradation. Thanks and Regards, Imran -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a\nmember of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
