On Mon, Feb 1, 2016 at 8:40 AM, Alexander Korotkov <aekorot...@gmail.com> wrote:
> I wonder if we can use 4-byte wait_event_info more efficiently.
> LWLock number in the tranche would be also useful information to expose.
> Using lwlock number user can determine if there is high concurrency for
> single lwlock in tranche or it is spread over multiple lwlocks.
> I think it would be enough to have 6 bits for event class id and 10 bit for
> event id. So, it would be maximum 64 event classes and maximum 1024 events
> per class. These limits seem to be fair enough for me.
> And then we save 16 bits for lock number. It's certainly not enough for some
> tranches. For instance, number of buffers could be easily more than 2^16.
> However, we could expose at least lower 16 bits. It would be at least
> something. Using this information user at least can make a conclusion like
> "It MIGHT be a high concurrency for single buffer content. Other way it is
> coincidence that a lot of different buffers have the same 16 lower bits.".
> Any thoughts?

Meh.  I think that's trying to be too clever.  That seems hard to
document, hard to explain, and likely incomprehensible to users.

Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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