Thread: O_NOATIME
Would people be interested in a trivial patch that adds O_NOATIME to open() for platforms that support it? (apparently Linux 2.6.8 and better). It seems to work here, feels harmless to me (an easy ifdef to check if it's there), and seems it would theoretically help, though I don't notice a consistent difference (I guess I"m not thrashing my disks hard enough?). Are there any open()s where we don't want NOATIME if available?
Ron Mayer <rm_pg@cheapcomplexdevices.com> writes: > Would people be interested in a trivial patch that adds O_NOATIME > to open() for platforms that support it? (apparently Linux 2.6.8 > and better). Isn't that usually, and more portably, handled in the filesystem mount options? regards, tom lane
Tom Lane wrote: > Ron Mayer <rm_pg@cheapcomplexdevices.com> writes: >> Would people be interested in a trivial patch that adds O_NOATIME >> to open() for platforms that support it? (apparently Linux 2.6.8 >> and better). > > Isn't that usually, and more portably, handled in the filesystem > mount options? Yes to both. I could imagine that for small systems/workstations you might have some files that want access time, and others that wanted NOATIME -- it seems the new flag lets you choose on a file-by-file bases. That's why I asked. I imagine it won't help on any well-administered production server since they'd probably mount the whole filesystem that way; but might help a bit on out-of-the-box-default-config benchmarks done by naive users who don't tweak filesystem settings. Don't know if we'd care about such an audience or not.
Ron Mayer <rm_pg@cheapcomplexdevices.com> writes: > Tom Lane wrote: >> Isn't that usually, and more portably, handled in the filesystem >> mount options? > Yes to both. I could imagine that for small systems/workstations > you might have some files that want access time, and others that > wanted NOATIME -- it seems the new flag lets you choose on a > file-by-file bases. Personally, if I were an admin who wanted access times, I'd regard the existence of such a flag as a security hole. regards, tom lane
Tom Lane wrote: > Ron Mayer <rm_pg@cheapcomplexdevices.com> writes: >> Tom Lane wrote: >>> Isn't that usually, and more portably, handled in the filesystem >>> mount options? > >> Yes to both. I could imagine that for small systems/workstations >> you might have some files that want access time, and others that >> wanted NOATIME -- it seems the new flag lets you choose on a >> file-by-file bases. > > Personally, if I were an admin who wanted access times, I'd regard > the existence of such a flag as a security hole. I'm not sure I see that. I'd have thought since postgresql already caches stuff in shared buffers, the atime of a postgresql file isn't reliable anyway; and outside of postgresql O_NOATIME doesn't seem to me to affect admins any worse the existence of utime(). OTOH, I'm not going to argue for the patch either. I think it'd be fair to say adding a linuxism and only benefiting novice/casual users isn't that exciting.