Bug 736433 - Bad scalability with memory cgroups.
Summary: Bad scalability with memory cgroups.
Status: CLOSED DUPLICATE of bug 717803
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.1
Hardware: Unspecified
OS: Unspecified
Target Milestone: rc
: ---
Assignee: Red Hat Kernel Manager
QA Contact: Red Hat Kernel QE team
Depends On:
TreeView+ depends on / blocked
Reported: 2011-09-07 16:54 UTC by Xavier Bru
Modified: 2011-09-09 11:35 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2011-09-09 11:35:35 UTC

Attachments (Terms of Use)

Description Xavier Bru 2011-09-07 16:54:30 UTC
Description of problem:

Bad scalability with memory cgroups.

Version-Release number of selected component (if applicable):

How reproducible:

run a program that allocates memory on a 32 cpu system

Steps to Reproduce:
1. create a user Memory Cgroup
2. run 32 occurences of program that allocates memory
3. compare time with same program executed outside Memory cgroup or with  cgroup_disable=memory
Actual results:

. in  cgroup memory:  
Time for Allocating Buffers : 100.222279 second(s)
 75.70%  _spin_lock res_counter_uncharge

Expected results:
. outside cgroup memory:
Time for Allocating Buffers : 3.721997 second(s) 

Additional info:
perf profiling shows contention on cgroup spinlock. This has been reworked in recent kernels to coalesce the accounting on cgroup. 2.6.37 kernel does not show the problem of scalability.

    75.70%  malloc_seq  [kernel.kallsyms]                                                                     [k] _s
            --- _spin_lock
               |--52.11%-- res_counter_uncharge
               |          __mem_cgroup_uncharge_common
               |          mem_cgroup_uncharge_page
               |          page_remove_rmap
               |          unmap_vmas
               |          exit_mmap
               |          mmput
               |          |          
               |          |--100.00%-- exit_mm
               |          |          do_exit
               |          |          do_group_exit
               |          |          sys_exit_group
               |          |          system_call_fastpath
               |           --0.00%-- [...]
               |--47.86%-- res_counter_charge

Comment 2 Gary Smith 2011-09-09 09:00:06 UTC

Is this the same issue as reported from Bull via myself at:

https://bugzilla.redhat.com/show_bug.cgi?id=717803  ?

Comment 3 Xavier Bru 2011-09-09 09:50:27 UTC
Yes,....Sorry I missed it was already opened as a Bugzilla.

Comment 4 Gary Smith 2011-09-09 11:35:35 UTC
No problem. I'll closed this BZ as a DUPLICATE of the other.

Can I ask you to please add the above information (and any additional data) as a new comment on the other BZ? (so that it is seen to come from an @bull.net address rather than an internal @redhat.com address).

*** This bug has been marked as a duplicate of bug 717803 ***

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