Re: Review: DTrace probes (merged version) ver_03

I performed review and I prepared own patch which contains only probes without
any issue. I suggest commit this patch because the rest of patch is independent
and it can be committed next commit fest after rework.

I found following issues:

1) SLRU probes.

I think it is good to have probes there but they needs polish. See my comments
http://reviewdemo.postgresql.org/r/25/

2) XLOG probes

I think there is confuse placement of probes after merge. It needs cleanup.

3) Executor probes

I would like to see any use case for them/

4) smgr probes

I prefer to have this probes in smgr instead of md. The reason why Robert put
them into md is that it returns number of written/read bytes, but it is "always"
BLCKSZ which could be returned from smgr directly. Only difference is
when error occurs during write/read and not all data are written/read.

It needs discuss.

5) autovacuum start probes

I would like to see also stat/stop for any other process types. It was discussed
but no comment from author(s).

6) idle transaction

See my comments
http://reviewdemo.postgresql.org/r/25/

7) query-reewrite is missing

8) mark dirty and BM_HINT... flag

I remove these because I don't see any use case for it. It would be nice provide
some dtrace script or describe basic ideas.

Thats all Zdenek