Re: Performance monitor signal handler

At 13:49 16/03/01 -0500, Jan Wieck wrote:
>
>    Similar problem as with shared  memory  -  size.  If  a  long
>    running  backend  of  a multithousand table database needs to
>    send access stats per table - and had accessed them all up to
>    now - it'll be alot of wasted bandwidth.

Not if you only send totals for individual counters when they change; some
stats may never be resynced, but for the most part it will work. Also, does
Unix allow interrupts to occur as a result of data arrivibg in a pipe? If
so, how about:

- All backends to do *blocking* IO to collector.

- Collector to receive an interrupt when a message arrives; while in the
interrupt it reads the buffer into a local queue, and returns from the
interrupt.

- Main line code processes the queue and writes it to a memory mapped file
for durability.

- If collector dies, postmaster starts another immediately, which slears
the backlog of data in the pipe and then remaps the file.

- Each backend has its own local copy of it's counters which *possibly* to
collector can ask for when it restarts.




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