Re: Thousands of parallel connections - Mailing list pgsql-general

From Chris Travers
Subject Re: Thousands of parallel connections
Date
Msg-id 41215469.9030608@travelamericas.com
Whole thread Raw
In response to Re: Thousands of parallel connections  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Tom Lane wrote:

>Chris Travers <chris@metatrontech.com> writes:
>
>
>>Tom Lane wrote:
>>
>>
>>>That does not add up: the graph can't have a negative y-intercept.
>>>There should be a substantial cost to run the postmaster at all,
>>>and then an essentially fixed cost per connection --- assuming
>>>that all the connections are running similar queries, of course.
>>>You're telling us the first 40 connections require zero RAM.
>>>
>>>
>
>
>
>>That is strange.  Is it really linear or does the cost go up somewhat
>>after the first few?
>>
>>
>
>Well, if you have significant contention problems then the speed could
>be worse than linear --- but he was talking about memory usage.  AFAICS,
>a backend doing a particular query should need X amount of RAM pretty
>much independently of how many others there are.  The only data structure
>I can think of that would be impacted at all is QuerySnapshot, and at
>4 bytes per sibling backend it's *way* down in the noise...
>
>            regards, tom lane
>
>---------------------------(end of broadcast)---------------------------
>TIP 8: explain analyze is your friend
>
>
>
>
Then my final question is whether part of the issue could be increased
shared memory and other performance related settings in order to
gracefully handle the larger number of connections.

Best Wishes,
Chris Travers
Metatron Technology Consulting

pgsql-general by date:

Previous
From: Tom Lane
Date:
Subject: Re: Thousands of parallel connections
Next
From: Tom Lane
Date:
Subject: Re: pg_clog and pg_xlog empty, postgresql refuses to start