I'd say the performance of a local in-process cache can be comparable with performance of OS cache only in one case: if your process is the only process in the system and no other files are read from disk. In all other (common) cases OS caches much larger set of data than is used by SQLite and naturally it will be harder for OS to find your data. Another concerns is if there is some other process reading/writing a lot from disk it will evict all your data from cache and you will have to read it from disk again. And one more observation: if you want to rely on OS cache every time you need your data you will have to make system call for reading. It's pretty expensive operation by itself, plus kernel does a lot more housekeeping operations than your application would do and kernel has a lot of different code paths dedicated for different use cases. If your application doesn't need all those use cases, those paths will just slow it down without giving any benefit.
So considering all that I'd say keeping your own local cache is always better than relying on something more general and intended for everybody to use (not just you). Pavel On Fri, Nov 19, 2010 at 9:44 PM, Yang <teddyyyy...@gmail.com> wrote: > I wonder why we need page cache, since we already have OS file cache. > > in other words, if we simply set OS cache to be very large, would it > have the same effect as page cache? > > thanks > Yang > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
