Re: high io BUT huge amount of free memory

From: Shaun Thomas <sthomas(at)optionshouse(dot)com>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Миша Тюрин <tmihail(at)bk(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: high io BUT huge amount of free memory
Date: 2013-04-24 14:06:39
Message-ID: 5177E6EF.5040902@optionshouse.com
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On 04/24/2013 08:49 AM, Andres Freund wrote:

> Uh. Ranting can be rather healthy thing every now and then and it good
> for the soul and such. But. Did you actually try reporting those issues?

That's actually part of the problem. How do you report:

Throwing a lot of processes at a high-memory system seems to break the
mm code in horrible ways.

I'm asking seriously here, because I have no clue how to isolate this
behavior. It's clearly happening often enough that random people are
starting to notice now that bigger servers are becoming the norm.

I'm also not a kernel dev in any sense of the word. My C is so rusty, I
can barely even read the patches going through the ML. I feel
comfortable posting to PG lists because that's my bread and butter.
Kernel lists seem way more imposing, and I'm probably not the only one
who feels that way.

I guess I don't mean to imply that kernel devs don't care. Maybe the
right way to put it is that there don't seem to be enough kernel devs
being provided with more capable testing hardware. Which is odd,
considering Red Hat's involvement and activity on the kernel.

I apologize, though. These last few months have been really frustrating
thanks to this and other odd kernel-related issues. We've reached an
equilibrium where the occasional waste of 20GB of RAM doesn't completely
cripple the system, but this thread kinda struck a sore point. :)

--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-676-8870
sthomas(at)optionshouse(dot)com

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