> > Since in your case all transactions A-E want the same buffer written, > > the memory (not it's content) will also be the same. > > But no, it won't: the successive writes will ask to write different > snapshots of the same buffer.
Successive writes would write different NON-OVERLAPPING sections of the same log buffer. It wouldn't make sense to send three separate copies of the entire block. That could indeed cause problems. If a separate log writing process was doing all the writing, it could pre-gang the writes. However, I'm not sure this is necessary. I'll test the simpler way first. > > The problem I can see offhand is how the kaio system can tell which > > transaction can be safely notified of the write, > > Yup, exactly. Whose snapshot made it down to (stable) disk storage? If you do as above, it can inform the transactions when the blocks get written to disk since there are no inconsistent writes. If transactions A, B and C had commits in block 1023, and the aio system writes that block to the disk, it can notify all three that their transaction write is complete when that block (or partial block) is written to disk. It transaction C's write didn't make it into the buffer, I've got to assume the aio system or the disk cache logic can handle realizing that it didn't queue that write and therefore not inform transaction C of a completion. - Curtis ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
