Re: Review: DTrace probes (merged version) ver_03

Greg Smith wrote:
> One tiny change I'd suggest here: if you look at the code for checkpoint
> buffer writing there are traces for two points in the process:
>
> CheckPointBuffers(int flags)
> {
> + TRACE_POSTGRESQL_BUFFER_CHECKPOINT_START(flags);
> CheckpointStats.ckpt_write_t = GetCurrentTimestamp();
> BufferSync(flags);
> CheckpointStats.ckpt_sync_t = GetCurrentTimestamp();
> smgrsync();
> CheckpointStats.ckpt_sync_end_t = GetCurrentTimestamp();
> + TRACE_POSTGRESQL_BUFFER_CHECKPOINT_DONE();
> }
>
> Note how the existing code also tracks how long the sync phase took
> compared to the write one, and reports both numbers in the checkpoint
> logs. It would be nice to add another probe at that same point (just
> after ckpt_sync_t is set) so that dtrace users could instrument all these
> possibilities as well: just buffer write time/resources, just sync ones,
> or both.

Sounds like the thing to do would be to pass CheckpointStats into the
DONE probe.

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Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.