On 2013-05-30 07:48:51 -0400, Greg Smith wrote: > On 5/30/13 7:17 AM, Andres Freund wrote: > >That argument in contrast I find not very convincing though. What was > >the last incidence of such a system call that did not just error out > >with ENOTSUPP or such? > > http://linux.die.net/man/2/posix_fadvise talks about POSIX_FADV_NOREUSE and > POSIX_FADV_WILLNEED being both buggy and quietly mapped to a no-op, > depending on your version. I know there were more examples than just that > one that popped up during the testing of effective_io_concurrency. My > starting position has to assume that posix_fallocate can have the same sort > of surprising behavior that showed up repeatedly when we were trying to use > posix_fadvise more aggressively.
Uh. How is that a correctness problem? fadvise is a hint which is pretty different from a fallocate where ignoring would have way much more severe consequences. I don't think that's a very meaningful comparison. > The way O_SYNC was quietly mapped to O_DSYNC (which isn't the same thing) > was a similar issue, and that's the first one that left me forever skeptical > of Linux kernel claims in this area until they are explicitly validated: > http://lwn.net/Articles/350225/ Yea, but that mistake is literally decades old... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers