lkml.org 
[lkml]   [2008]   [Jul]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2.6.26-rc8-mm1] memrlimit: fix mmap_sem deadlock
On Fri, 04 Jul 2008 08:50:47 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> > I was referring to the below (which is where the conversation ended).
> >
> > It questions the basis of the whole feature.
> >
>
> In the email below, I referred to Hugh's comment on tracking total_vm as a more
> achievable target and it gives a rough approximation of something worth
> limiting. I agree with him on those points and mentioned my motivation for the
> memrlimit patchset. We also look forward to enhancing memrlimit to control
> mlock'ed pages (as it provides the generic infrastructure to control RLIMIT'ed
> resources). Given Hugh's comment, I looked at it from the more positive side
> rather the pessimistic angle. I've had discussions along these lines with Paul
> Menage and Kamezawa. In the past we've discussed and there are cases where
> memrlimit is not useful (large VM allocations with sparse usage), but there are
> cases as mentioned below in the motivation for memrlimits as to why and where
> they are useful.
>
> If there are suggestions to help improve the feature or provide similar
> functionality without the noise; I am all ears

Well I've never reeeeeeealy understood what the whole feature is for.

+Advantages of providing this feature
+
+1. Control over virtual address space allows for a cgroup to fail gracefully
+ i.e., via a malloc or mmap failure as compared to OOM kill when no
+ pages can be reclaimed.
+2. It provides better control over how many pages can be swapped out when
+ the cgroup goes over its limit. A badly setup cgroup can cause excessive
+ swapping. Providing control over the address space allocations ensures
+ that the system administrator has control over the total swapping that
+ can take place.

umm, OK. I'm not sure _why_ someone would want to do that. Perhaps
some use-cases would help motivate us. Perhaps desriptions of
real-world operational problems would would be improved or solved were
this feature available to the operator.



\
 
 \ /
  Last update: 2008-07-04 06:29    [W:0.334 / U:0.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site