On 2016-02-11 07:06, Christopher Samuel wrote:
On 11/02/16 06:15, Christopher B Coffey wrote: > I’m curious which kernel you are running on your el6 clusters that > have cgroups enabled in slurm. I have an issue where some workloads > cause 100’s-1000’s of flocks to occur relating to the memory cleanup > portion in the cgroup. This is kernel code, or userspace? My understanding of the kernel developers concerns over memory cgroups was around the extra overhead in memory allocation inside the kernel. Here's a write up from LWN from the 2012 mm minisummit at the Kernel Summit on the issue: https://lwn.net/Articles/516533/ Interestingly the RHEL page mentions a memory overhead on x86-64. but not a performance issue, so whether they backported later patches to reduce the impact of memory cgroups I cannot tell right now. https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Resource_Management_Guide/sec-memory.html I did benchmarking a few years back when were transitioning to RHEL6 and Slurm with memory cgroups enabled and couldn't see any significant difference in performance. Unfortunately I suspect I cleaned all that up some time ago. :-( We use them and haven't noticed any issues yet. All the best, Chris
See http://slurm.schedmd.com/slurm_ug_2012/SUG-2012-Cgroup.pdf slides 31-35. I don't know if RedHat has backported the 2.6.38 memcg changes to the 2.6.32 version they use in RHEL6. -- Janne Blomqvist, D.Sc. (Tech.), Scientific Computing Specialist Aalto University School of Science, PHYS & NBE +358503841576 || [email protected]
