> On Apr 12, 2016, at 10:20 PM, Andres Freund <and...@anarazel.de> wrote: > > 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. I’ll double check in the morning, but i did copy it from the log.
> Could you show a strace of a failed start with an > unmodified postgres? we didn’t have the error when not using huge_pages. >> 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. Well all i have at the moment is that when we disabled huge pages on the kernel level and then restarted postgres there were no additional crashes. Unfortunately I cannot access the server now. I will look further tomorrow. > > > Greetings, > > Andres Freund Sincerely, Reiner Peterke -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
