Simon, On 3/12/07 6:21 AM, "Simon Riggs" <[EMAIL PROTECTED]> wrote:
> So based on those thoughts, sync_scan_offset should be fixed at 16, > rather than being variable. In addition, ss_report_loc() should only > report its position every 16 blocks, rather than do this every time, > which will reduce overhead of this call. And for N concurrent scans? I think there is actually no need to synchronize the shared buffers at all for synchronized scans. The OS I/O cache will do that for us and we're just going to interfere and pessimize by trying to divide up a local buffer. I suggest that this be proven or disproved by running this test: measure the performance of syncscan with the non-polluting buffer change, then measure with Jeff's patch and non-polluting with multiple scans, then measure with your suggested changes to synchronize the buffers. Somewhere in that progression we'll learn more about how the multi-level buffering really works. I think we'll get all the shared I/O cache we need. - Luke ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
