On 01/06/2012 02:33 PM, KOSAKI Motohiro wrote: > (1/6/12 1:30 AM), Tao Ma wrote: >> On 01/06/2012 02:18 PM, KOSAKI Motohiro wrote: >>> 2012/1/6 Tao Ma<tm@xxxxxx>: >>>> Hi Kosaki, >>>> On 12/30/2011 06:07 PM, KOSAKI Motohiro wrote: >>>>>>> Because your test program is too artificial. 20sec/100000times = >>>>>>> 200usec. And your >>>>>>> program repeat mlock and munlock the exact same address. so, yes, if >>>>>>> lru_add_drain_all() is removed, it become near no-op. but it's >>>>>>> worthless comparision. >>>>>>> none of any practical program does such strange mlock usage. >>>>>> yes, I should say it is artificial. But mlock did cause the >>>>>> problem in >>>>>> our product system and perf shows that the mlock uses the system time >>>>>> much more than others. That's the reason we created this program >>>>>> to test >>>>>> whether mlock really sucks. And we compared the result with >>>>>> rhel5(2.6.18) which runs much much faster. >>>>>> >>>>>> And from the commit log you described, we can remove >>>>>> lru_add_drain_all >>>>>> safely here, so why add it? At least removing it makes mlock much >>>>>> faster >>>>>> compared to the vanilla kernel. >>>>> >>>>> If we remove it, we lose to a test way of mlock. "Memlocked" field of >>>>> /proc/meminfo >>>>> show inaccurate number very easily. So, if 200usec is no avoidable, >>>>> I'll ack you. >>>>> But I'm not convinced yet. >>>> Do you find something new for this? >>> >>> No. >>> >>> Or more exactly, 200usec is my calculation mistake. your program call >>> mlock >>> 3 times per each iteration. so, correct cost is 66usec. >> yes, so mlock can do 15000/s, it is even slower than the whole i/o time >> for some not very fast ssd disk and I don't think it is endurable. I >> guess we should remove it, right? Or you have another other suggestion >> that I can try for it? > > read whole thread. I have read the whole thread, and you just described that the test case is artificial and there is no suggestion or patch about how to resolve it. As I have said that it is very time-consuming and with more cpu cores, the more penalty, and an i/o time for a ssd can be faster than it. So do you think 66 usec is OK for a memory operation? Thanks Tao -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>