On 01/10/2012 07:58 AM, KOSAKI Motohiro wrote: > (1/6/12 1:46 AM), Tao Ma wrote: >> 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? > > I don't think you've read the thread at all. please read akpm's commnet. > > http://www.spinics.net/lists/linux-mm/msg28290.html Oh, your patch set doesn't cc to me, so my mail filter moved it to another directory.. Sorry and I will read the whole thread. Thanks again for your time. 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>