| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tv(at)fuzzy(dot)cz>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: 9.5: Better memory accounting, towards memory-bounded HashAgg |
| Date: | 2014-11-17 16:14:34 |
| Message-ID: | CA+U5nMKeafiSUTR=gMkQfAAZwmrRmbr=7ga8Xk3hdbkvKo8Kuw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 17 November 2014 07:31, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> To calculate the total memory used, I included a function
> MemoryContextMemAllocated() that walks the memory context and its
> children recursively.
If we assume that we want the results accurate to within 5%, then we
can work out a good sampling rate to achieve that accuracy.
We would probably need a counting mechanism that didn't slow down O(N)
as our allocations get bigger.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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