Engineering topics

McCrea, A.

Publications and source records attributed to McCrea, A..

5 records

DOE OSTI2015

Pushing HTCondor and glideinWMS to 200K+ Jobs in a Global Pool for CMS before Run 2

The CMS experiment at the LHC relies on HTCondor and glideinWMS as its primary batch and pilot-based Grid provisioning system. So far we have been running several independent resource pools, but we are working on unifying them all to reduce the operational load and more effectively share resources between various activities in CMS. The major challenge of this unification activity is scale. The combined pool size is expected to reach 200K job slots, which is significantly bigger than any other multi-user HTCondor based system currently in production. To get there we have studied scaling limitations in our existing pools, the biggest of which tops out at about 70K slots, providing valuable feedback to the development communities, who have responded by delivering improvements which have helped us reach higher and higher scales with more stability. We have also worked on improving the organization and support model for this critical service during Run 2 of the LHC. This contribution will present the results of the scale testing and experiences from the first months of running the Global Pool.

Balcas, J.↗

DOE OSTI2015

Using the GlideinWMS System as a Common Resource Provisioning Layer in CMS

CMS will require access to more than 125k processor cores for the beginning of Run 2 in 2015 to carry out its ambitious physics program with more and higher complexity events. During Run1 these resources were predominantly provided by a mix of grid sites and local batch resources. During the long shut down cloud infrastructures, diverse opportunistic resources and HPC supercomputing centers were made available to CMS, which further complicated the operations of the submission infrastructure. In this presentation we will discuss the CMS effort to adopt and deploy the glideinWMS system as a common resource provisioning layer to grid, cloud, local batch, and opportunistic resources and sites. We will address the challenges associated with integrating the various types of resources, the efficiency gains and simplifications associated with using a common resource provisioning layer, and discuss the solutions found. We will finish with an outlook of future plans for how CMS is moving forward on resource provisioning for more heterogenous architectures and services.

Balcas, J.↗

DOE OSTI2015

Evolution of CMS Workload Management Towards Multicore Job Support

The successful exploitation of multicore processor architectures is a key element of the LHC distributed computing system in the coming era of the LHC Run 2. High-pileup complex-collision events represent a challenge for the traditional sequential programming in terms of memory and processing time budget. The CMS data production and processing framework is introducing the parallel execution of the reconstruction and simulation algorithms to overcome these limitations. CMS plans to execute multicore jobs while still supporting singlecore processing for other tasks difficult to parallelize, such as user analysis. The CMS strategy for job management thus aims at integrating single and multicore job scheduling across the Grid. This is accomplished by employing multicore pilots with internal dynamic partitioning of the allocated resources, capable of running payloads of various core counts simultaneously. An extensive test programme has been conducted to enable multicore scheduling with the various local batch systems available at CMS sites, with the focus on the Tier-0 and Tier-1s, responsible during 2015 of the prompt data reconstruction. Scale tests have been run to analyse the performance of this scheduling strategy and ensure an efficient use of the distributed resources. This paper presents the evolution of the CMS job management and resource provisioning systems in order to support this hybrid scheduling model, as well as its deployment and performance tests, which will enable CMS to transition to a multicore production model for the second LHC run.

Perez-Calero Yzquierdo, A.↗

DOE OSTI2014

Evolution of the pilot infrastructure of CMS: towards a single glideinWMS pool

CMS production and analysis job submission is based largely on glideinWMS and pilot submissions. The transition from multiple different submission solutions like gLite WMS and HTCondor-based implementations was carried out over years and is coming now to a conclusion. The historically explained separate glideinWMS pools for different types of production jobs and analysis jobs are being unified into a single global pool. This enables CMS to benefit from global prioritization and scheduling possibilities. It also presents the sites with only one kind of pilots and eliminates the need of having to make scheduling decisions on the CE level. This paper provides an analysis of the benefits of a unified resource pool, as well as a description of the resulting global policy. It will explain the technical challenges moving forward and present solutions to some of them.

Belforte, S.↗

DOE OSTI2014

Opportunistic Resource Usage in CMS

CMS is using a tiered setup of dedicated computing resources provided by sites distributed over the world and organized in WLCG. These sites pledge resources to CMS and are preparing them especially for CMS to run the experiment's applications. But there are more resources available opportunistically both on the GRID and in local university and research clusters which can be used for CMS applications. We will present CMS' strategy to use opportunistic resources and prepare them dynamically to run CMS applications. CMS is able to run its applications on resources that can be reached through the GRID, through EC2 compliant cloud interfaces. Even resources that can be used through ssh login nodes can be harnessed. All of these usage modes are integrated transparently into the GlideIn WMS submission infrastructure, which is the basis of CMS' opportunistic resource usage strategy. Technologies like Parrot to mount the software distribution via CVMFS and xrootd for access to data and simulation samples via the WAN are used and will be described. We will summarize the experience with opportunistic resource usage and give an outlook for the restart of LHC data taking in 2015.

Kreuzer, Peter↗