Re: doc patch - linux memory handling - Mailing list pgsql-patches

From Andrew Dunstan
Subject Re: doc patch - linux memory handling
Date
Msg-id 3F46505B.7080101@dunslane.net
Whole thread Raw
In response to Re: doc patch - linux memory handling  (Peter Eisentraut <peter_e@gmx.net>)
List pgsql-patches
It's highly unsatisfactory, but it's a fact nonetheless. The stock
kernel simply checks for a non-zero value in this variable and says "OK,
give them the memory" if it finds it. So if you are using such a kernel,
then setting the non-zero value turns off all checking, rather than
using the default heuristic check. That's why advising people to use a
value of, say, 3, is so dangerous. Go and read the source if you don't
believe me.

Actually, I've had some success with both vendors and experts. Far more
than I have with vendors of proprietary software. But YMMV. The point,
though, is that this is not our problem, as I see it.

andrew



Peter Eisentraut wrote:

>Andrew Dunstan writes:
>
>
>
>>+        <para>
>>+       Warning: using these settings in a kernel which does not support
>>+       these modes will almost certainly increase the danger of the
>>+       kernel killing the postmaster, rather than reducing it.
>>+       If in any doubt, consult a kernel expert or your kernel vendor.
>>+       </para>
>>
>>
>
>If find this a bit unsatisfactory.  If the kernel does not support these
>modes, then "using" them should have no effect.  At least, since the
>kernel doesn't know what they mean, the danger of a postmaster kill cannot
>increase.
>
>Oh, and have you ever tried to contact a kernel expert or kernel vendor?
>:-)
>
>
>



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