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? 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>