On Fri, Aug 10, 2012 at 4:43 PM, Black, Michael (IS) <[email protected] > wrote:
> Why should shared cached be serialized when all the threads are reading? > I can see it for writing, but not just for reading. There must be some > logic that be done to allow this I would think (he said without looking at > the code). > The cache is written as content is loaded off of disk. > > Michael D. Black > Senior Scientist > Advanced Analytics Directorate > Advanced GEOINT Solutions Operating Unit > Northrop Grumman Information Systems > > ________________________________________ > From: [email protected] [[email protected]] > on behalf of Richard Hipp [[email protected]] > Sent: Friday, August 10, 2012 12:53 PM > To: General Discussion of SQLite Database > Subject: EXT :Re: [sqlite] Multi-Thread Reads to SQLite Database > > On Fri, Aug 10, 2012 at 12:18 PM, esum <[email protected]> wrote: > > > > > However, when I ran this same test with SQLITE_OPEN_READWRITE | > > SQLITE_OPEN_SHAREDCACHE for the flags, I get the following [slower] > > results: > > > > Why am I seeing such a high increase in times as I add threads in shared > > cache mode as opposed to without it? > > > > In shared-cache mode, the page cache is shared across threads. That means > that each thread must acquire a mutex on the page cache in order to read > it. Which means that access to the page cache is serialized. > > > -- > D. Richard Hipp > [email protected] > _______________________________________________ > sqlite-users mailing list > [email protected] > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ > sqlite-users mailing list > [email protected] > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- D. Richard Hipp [email protected] _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
