| From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, 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 20:45:26 |
| Message-ID: | CAHyXU0wBiYz1nAHRho-4m4AYNdPm8_wsxud5GqnQ_rGe9uVkEQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jan 5, 2012 at 2:25 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> 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.
likewise (champion bikeshedder here). It just so happens I typically
set 'large' server shared memory to 256mb.
merlin
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