On 2016-04-12 21:58:14 +0200, reiner peterke wrote: > Hi > > We have been doing some testing with Postgres (9.5.2) compiled on a Power8 > running Centos 7 > > When working with huge_pages, we initially got this error. > > munmap(0x3efbe4000000) failed: Invalid argument
*munmap*, not mmap failed? that's odd; because there the hugepagesize shouldn't have much of an influence. If something fails it should be the initial mmap. Could you show a strace of a failed start with an unmodified postgres? > after a bit of investigation we noticed that hugepagesize is har coded > to 2MB Note it's not actually hardcoded to some size. It's just about rounding the size to a multiple of 2MB due to an older kernel bug: /* * Round up the request size to a suitable large value. * * Some Linux kernel versions are known to have a bug, which causes * mmap() with MAP_HUGETLB to fail if the request size is not a * multiple of any supported huge page size. To work around that, we * round up the request size to nearest 2MB. 2MB is the most common * huge page page size on affected systems. > Going further, we tried testing hugepages also on Ubuntu 16.04, also on the > power8. On Ubuntu Postgres did not like the hugepages at all (set also to > 16MB) and consistently crashed. > Looking for some insight into this issue. the error from the postgres > log on ubuntu is below. It apperas to be related to semephores. I've a bit of a hard time believing that this is related to huge pages. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers