| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: CLOG contention |
| Date: | 2012-01-05 20:25:51 |
| Message-ID: | CA+TgmoagzcQR69nSRDHygSggfJiKLWFhunw=uToZga5bWw5SiA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jan 5, 2012 at 2:44 PM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> If we go with such a formula, I think 32 MB would be a more
> appropriate divisor than 128 MB. Even on very large machines where
> 32 CLOG buffers would be a clear win, we often can't go above 1 or 2
> GB of shared_buffers without hitting latency spikes due to overrun
> of the RAID controller cache. (Now, that may change if we get DW
> in, but that's not there yet.) 1 GB / 32 is 32 MB. This would
> leave CLOG pinned at the minimum of 8 buffers (64 KB) all the way up
> to shared_buffers of 256 MB.
That seems reasonable to me.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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