On Tue 04-01-11 05:21:46, CAI Qian wrote: > > > > 3) overcommit 2gb hugepages. > > > mmap(NULL, 18446744071562067968, PROT_READ|PROT_WRITE, MAP_SHARED, > > > 3, 0) = -1 ENOMEM (Cannot allocate memory) > > > > Hmm, you are trying to reserve/mmap a lot of memory (17179869182 1GB > > huge pages). > That is strange - the test code merely did this, > addr = mmap(ADDR, 2<<30, PROTECTION, FLAGS, fd, 0); Didn't you want 1<<30 instead? > > Do you know if overcommit was designed for 1GB pages? At least, read this > from Documentation/kernel-parameters.txt, > > hugepagesz= > ... > Note that 1GB pages can only be allocated at boot time > using hugepages= and not freed afterwards. > > How does it allow to be overcommitted for only being able to allocate at > boot time? Sorry, I am not very much familiar with 1GB pages but the hugetlb code is not page size specific AFAICS so if there are no other background things than it should just work. > > > > Also, nr_overcommit_hugepages was overwritten with such a strange > > > value after overcommit failure. Should we just remove this file from > > > sysfs for simplicity? > > > > This is strange. The value is set only in hugetlb_overcommit_handler > > which is a sysctl handler. > > > > Are you sure that you are not changing the value by the /sys interface > > somewhere (there is no check for the value so you can set what-ever > > value you like)? I fail to see any mmap code path which would change > > this value. > I could double-check here, but it is not important if the fact is that > overcommit is not supported for 1GB pages. What is the complete test case? > > > Btw. which kernel version are you using. > mmotm 2010-12-02-16-34 version 2.6.37-rc4-mm1+. This problem is also present > in 2.6.18. > > Thanks. > > CAI Qian > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxxx For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Michal Hocko L3 team SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>