On Tue, Apr 19, 2005 at 04:48:38PM -0400, Marc E. Fiuczynski wrote:
> Hi Chandra,
>
> The following program will be killed in our system by the memory controller
> (both the E17 based one and a prior one):
>
> dd bs=4096 count=250000 < /dev/zero > /bigfile
>
> The class within which this command executes is setup as follows:
>
> res=mem,guarantee=-2,limit=125000,total_guarantee=100,max_limit=100
>
> The default class has the following:
>
> res=mem,guarantee=-2,limit=-2,total_guarantee=322735,max_limit=322735
That is bad behavior....
Have you played with the config parameters to see if it helps ?
>
> Is it really the case that dd consumes that much memory and therefore must
> be killed? I think this is unlikely, as observing its VIRT and RSS from the
> top output shows that its size does not grow beyond a few megabytes.
Yes, its RSS/VIRT doesn't increase... but those are not what we are
accounting....
We account the pages that come into lru list(active/inactive)....
May be the controller should also follow RSS and usage of the class and be
aggressive in cleaning up the active inactive lists. I 'll think about it.
>
> Or, is the memory controller keeping track of pages that logically no longer
> belong to the class. Looking at output of dmesg, I see the following
> bef_shnk_cls and aft_shnk_cls debug messages:
>
=== stuff deleted ===
>
> Not sure how to interpret this exactly, but it seems me that the bulk of the
> pages are in the inae/lina lists. Maybe the mem controller should be more
> aggressive in cleaning out these lists before killing a process like dd.
The logic is purposely simple and less-intrusive... If a class is over its
limit,
then we try to bring the class's (lru list's) usage to a level (as specified in
the config file) by using the VM subsystem's shrink logic.
There are few problems if we aggressively cleanup the lru lists.
- we may be throwing the pages out which may be pulled in by the task in
very near future.
- if a class need lot more than the limit, we will be swapping bigtime
to
the disk, which would slow down the other processes in the system
We cannot differentiate the above dd case with a legitimate use of a
class(unless
we monitor the RSS usage as mentioned above).
Comments, Suggestions welcome.
>
> Marc
>
>
>
>
>
--
----------------------------------------------------------------------
Chandra Seetharaman | Be careful what you choose....
- [EMAIL PROTECTED] | .......you may get it.
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