Subject: Re: [vserver] Trying to understand vserver memory
From: "Belinda Lawson" <briffee@gmail.com>
Date: Thu, 24 Jan 2008 14:11:42 -0800
Thu, 24 Jan 2008 14:11:42 -0800
Hi, Dallas.  Thanks for your reply.   I am currently trying to set my soft
limit to 256 (65536 pages?) and my hard limit to 512 (131072 pages?)  and I
am finding that the documentation says that I should be able to do that
using files like this:

soft limit in a file called rss
hard limit in a file called rss.hard

However, in this case, only my hard limit is being honored when I restart my
vserver.  Does that make any sense?  Perhaps I missed something.  I can
successfully go back and set it with the vlimit command after the vserver
starts, but the files aren't doing what I would expect on startup.

Thanks again,
-Belinda

On Jan 24, 2008 10:16 AM, Dallas Kashuba <dallas@dreamhost.com> wrote:

> Here's my understanding:
>
> If you want 256M of ram and 256M of swap, you want to set rss soft
> limit to 256MB and rss hard limit to 512MB (the sum of both ram and
> swap).  We also set the as limits adequately high.
>
> Hopefully that helps,
>        Dallas
>
> On Jan 23, 2008, at 10:15 PM, Belinda Lawson wrote:
>
> > Hi, I need a bit of help understanding how memory management works
> > inside a vserver.  My problem is that I would like to mimic the
> > behavior of a unix system with 256M ram and 256M swap.  I have read
> > the documentation on the wiki, but I am still not certain how to
> > mimic the behavior of swap.
> >
> > In my experiments, if I set the rss hard limit to 256M to reflect
> > the physical ram, it begins to kill processes (somewhat randomly?)
> > if more than 256M is requested, rather than allow swap to be used.
> > In fact, I never see swap used at all, which is very strange since
> > `free` reports that swap does exist inside the vserver.   Could you
> > help me understand how I can adjust the rss and as limits to get
> > behavior more in line with my goal?
> >
> > Thanks, in advance, for any enlightenment you can provide.
> >
> > Best regards,
> > -Belinda
>
>


Hi, Dallas.  Thanks for your reply.   I am currently trying to set my soft limit to 256 (65536 pages?) and my hard limit to 512 (131072 pages?)  and I am finding that the documentation says that I should be able to do that using files like this:

soft limit in a file called rss
hard limit in a file called rss.hard

However, in this case, only my hard limit is being honored when I restart my vserver.  Does that make any sense?  Perhaps I missed something.  I can successfully go back and set it with the vlimit command after the vserver starts, but the files aren't doing what I would expect on startup.

Thanks again,
-Belinda

On Jan 24, 2008 10:16 AM, Dallas Kashuba <dallas@dreamhost.com> wrote:
Here's my understanding:

If you want 256M of ram and 256M of swap, you want to set rss soft
limit to 256MB and rss hard limit to 512MB (the sum of both ram and
swap).  We also set the as limits adequately high.

Hopefully that helps,
       Dallas

On Jan 23, 2008, at 10:15 PM, Belinda Lawson wrote:

> Hi, I need a bit of help understanding how memory management works
> inside a vserver.  My problem is that I would like to mimic the
> behavior of a unix system with 256M ram and 256M swap.  I have read
> the documentation on the wiki, but I am still not certain how to
> mimic the behavior of swap.
>
> In my experiments, if I set the rss hard limit to 256M to reflect
> the physical ram, it begins to kill processes (somewhat randomly?)
> if more than 256M is requested, rather than allow swap to be used.
> In fact, I never see swap used at all, which is very strange since
> `free` reports that swap does exist inside the vserver.   Could you
> help me understand how I can adjust the rss and as limits to get
> behavior more in line with my goal?
>
> Thanks, in advance, for any enlightenment you can provide.
>
> Best regards,
> -Belinda