Jan Wieck wrote:Bruce Momjian wrote:
> Jan Wieck wrote:
>> Bruce Momjian wrote:
>> >> > Now, O_SYNC is going to force every write to the disk. If we have a
>> > transaction that has to write lots of buffers (has to write them to
>> > reuse the shared buffer)
>> >> So make the background writer/checkpointer keeping the LRU head clean. I >> explained that 3 times now.
> > If the background cleaner has to not just write() but write/fsync or
> write/O_SYNC, it isn't going to be able to clean them fast enough. It
> creates a bottleneck where we didn't have one before.
> > We are trying to eliminate an I/O storm during checkpoint, but the
> solutions seem to be making the non-checkpoint times slower.
>
It looks as if you're assuming that I am making the backends unable to write on their own, so that they have to wait on the checkpointer. I never said that.
Maybe I missed it but are those backend now doing write or write/fsync? If the former, that is fine. If the later, it does seem slower than it
used to be.
In my all_performance.v4.diff they do write and the checkpointer does write+sync.
Jan
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