On Fri 31-12-10 06:08:21, CAI Qian wrote: > Hi, Hi, > > Problem: nr_overcommit_hugepages for 1gb hugepage went crazy. > > Symptom: > 1) setup 1gb hugepages. > # cat /proc/cmdline > default_hugepagesz=1g hugepagesz=1g hugepages=1 > # cat /proc/meminfo > ... > HugePages_Total: 1 > HugePages_Free: 1 > HugePages_Rsvd: 0 > HugePages_Surp: 0 > Hugepagesize: 1048576 kB > ... > > 2) set nr_overcommit_hugepages > # echo 1 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages > # cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages > 1 > > 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). > # cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages > 18446744071589420672 > > As you can see from the above, it did not allow overcommit despite nr_overcommit_hugepages value. You are trying to allocate much more than your overcommit allows. > 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. Btw. which kernel version are you using. > > Thanks. > > CAI Qian Regards -- 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>