On Thu, Mar 8, 2012 at 9:28 AM, Pavel Ivanov <paiva...@gmail.com> wrote: >> Question: Does anybody know of a better way to get memory shared among >> processes other than to create a fake file and mmap() it? Are there some >> magic options to mmap() (perhaps Linux-only options) that prevent it from >> actually writing to disk? > > Why don't you use shm_open() instead of a real file? I'm not sure > though how it behaves with chroot jail.
I do not recall the full semantics of shm_open(), but I _think_ that it shares the sysv shared-memory problem where the memory sticks around until explicitly deleted. Using a fake file with mmap() will create a segment which only exists until the last process using it goes away. This can become a resource issue on some systems. Also, the name would have to be carefully constructed to prevent conflicts, as the namespace may not be the same as the file path namespace (even path-like names may have different length restrictions). Like maybe base64(hash(canonical_path(dbpath))). BTW, the SQLite docs indicate that as of 3.7.4, you can arrange to use an exclusive mode which allows WAL to work without shm. That may be a reasonable approach for some subset of users with this kind of problem. -scott _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
