Re: Patch: fix lock contention for HASHHDR.mutex - Mailing list pgsql-hackers

From Aleksander Alekseev
Subject Re: Patch: fix lock contention for HASHHDR.mutex
Date
Msg-id 20151218081009.34ea4c04@fujitsu
Whole thread Raw
In response to Re: Patch: fix lock contention for HASHHDR.mutex  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: Patch: fix lock contention for HASHHDR.mutex
List pgsql-hackers
> Oh, that's an interesting idea.  I guess the problem is that if the
> freelist is unshared, then users might get an error that the lock
> table is full when some other partition still has elements remaining.

True, but I don't believe it should be a real problem assuming we have
a strong hash function. If user get such an error it means that
database is under heavy load and there is not much more free elements
in other tables either. This particular user didn't get lucky, some
other will. Anyway administrator should do something about it -
fight DDoS attack, tune database parameters, etc.

> 3.5-4 more TPS, or 3.5 times more TPS?  Can you share the actual
> numbers?

Oops, 3.5-4 _times_ more TPS, i.e. 2206 TPS vs 546 TPS.



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