>> It would be also interesting if "reads" exposed in various places (isql, >> monitoring tables, trace api) are pure physical reads from disk and/or >> fetched from the OS file system cache. >> >> I guess, it could be also from the file system cache, because I've seen >> situations where execution time is larger for the same number of >> physical reads for a newly established connection, which then decreases >> for sub-sequent execution of the same statement with an equal number of >> reads. > > There is no way to know if OS resolved read request from cache or from > disk.
Thought so that Firebird can't differ here. Just speaking out loud that if execution time for the same statement is a fraction with the same number of physical reads, then data is probably coming from the file system cache instead of the disk. A perfect use case for the Trace API to detect such things. > Even if application is used so called "direct IO" read request could be > resolved > from file cache - if some other application reads same file using file cache > few > moments before. Yup. Thanks, Thomas ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
