----- Original Message ----- > On Tue, 04 Jan 2011, CAI Qian wrote: > > > 1GB pages cannot be over-commited, attempting to do so results in > > corruption, > > so remove those files for simplicity. > > > > Symptoms: > > 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) > > > > cat > > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_overcommit_hugepages > > 18446744071589420672 > > > > Signed-off-by: CAI Qian <caiqian@xxxxxxxxxx> > > There are a couple of issues here: first, I think the overcommit value > being overwritten > is a bug and this needs to be addressed and fixed before we cover it > by removing the sysfs > file. > > Second, will it be easier for userspace to work with some huge page > sizes having the > overcommit file and others not or making the kernel hand EINVAL back > when nr_overcommit is > is changed for an unsupported page size? > > Finally, this is a problem for more than 1GB pages on x86_64. It is > true for all pages > > 1 << MAX_ORDER. Once the overcommit bug is fixed and the second issue > is answered, the > solution that is used (either EINVAL or no overcommit file) needs to > happen for all cases > where it applies, not just the 1GB case. I have a new patch ready to return EINVAL for both sysfs/procfs, and will reject changing of nr_hugepages. Do you know if nr_hugepages_mempolicy is supposed to be able to change in this case? It is not possible currently. # cat /proc/sys/vm/nr_hugepages_mempolicy 1 # echo 0 >/proc/sys/vm/nr_hugepages_mempolicy # cat /proc/sys/vm/nr_hugepages_mempolicy 1 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>