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description: GSI Helmholtzzentrum für Schwerionenforschung
items: Meeting on Thursday, April 26, 2007
items: Re: Meeting on Thursday, April 26, 2007

Meeting on Thursday, April 26, 2007
type: item
description: ALICE Computing Meeting April 26, 2007 Preliminary agenda: 1. Origin of high failing rate of Alien jobs at GSI How to proceed - 1.1 Detection of problem 1.2 Responsible from KP1 group to fix possible problems, if they are AliRoot related 1.3 What tools can we use to detect problems (see informations below) 2. Alien SE at GSI 2.1 How to make it working? - Responsible? 2.2 Can we use it already for staging of the fraction of PDC06 data? 3. XRD copy (see informations below) ============================================================== VERY QUICK MINUTES (27.04.2007, Silvia) We discussed only point 1. a. currently only one GRID job at the time can run on the D-Grid machines, despite their 8GB memory (but only 2GB swap). Silvia will test some parallel running of AliRoot jobs executed in "stand-alone" mode instead of via AliEn (see how many jobs per machine can run, and when/where the memory limits are reached) b. we decided to postpone further investigations about that fact that GRID jobs cannot be executed on the batch farm to when Kilian will be back at GSI c. Marian and Silvia will investigate the memory consumption of AliRoot during a typical simulation+reconstruction job (using tools like valgrind). Possible problems (like memory leaks) will be reported to the software/ detector responsibles. Below, please, find quite some material collected about the memory consumption of AliRoot GRID jobs and details of the failures happening when copying to the xrootd cluster. No formal meeting will take place in the next 2 weeks. Information and results will be distributed via the forum and emails. ============================================================== INFORMATION ABOUT THE GRID JOBS AT GSI 1 -- STATUS AS REPORTED BY MONALISA 1.1 Summary table for all centers: see http://pcalimonitor.cern.ch:8889/reports/index.jsp (in daily, weekly, monthly summaries) 1.2 Integrated CPU time for ALICE jobs at GSI compared to Muenster, Catania and FKZ (the pledged resources of these cent…
creator: Silvia Masciocchi
date: 2007-04-25T14:31:09-00:00

Re: Meeting on Thursday, April 26, 2007
type: item
description: Dear Silvia and all, I would like to comment your points: 1. from the summary table one can see that GSI dedicated 100 CPUs to Grid computing, which we did not fullfill so far. But we will certainly come close to that within this year. Especially when you compute the number of 100 CPUs into kSi2k of the time when this number has been pledged. 2. you reported nothing about failure rates at GSI. what you reported is: - integrated CPU time at GSI compared to other centres. This value compares more or less with the percentual site share, which has been 4 to 5% at Muenster and 0.5% at GSI so far. The reason for this is that we have been running continuously 3 Grid jobs at GSI for quite some time (and most of them successfully and without failures !!!) since the high mem queue did not provide more than 3 machines in the batch farm and the other batch machines were not able to deal with the memory consumption of ALICE jobs. Since we put the D-Grid machines into production we run 10 jobs in average in parallel, which is already a significant improvement. We also tried already 2 jobs in parallel but the efficiency of job performance became definitely worse compared to only 1 job per machine. The reason might be found out by continous local job monitoring. According to our preliminary findings the peak of memory consumption, which happens only for a short while during reconstruction, may exceed the machine capabiliies when two jobs are running at the same time having the peak roughly at the same time, too. In any case if the integrated CPU time at GSI compares with the percentual share of jobs running at GSI then the failure rate at GSI also compares with other sites. Memory consumption of ALICE jobs at 64bit machines used to be significantly higher than at non 64bit machines with former AliRoot versions. This improved slightly with newer AliRoot versions. If you compare the memory of GSI batch machines with other machines then please consider that our machines rarely have SW…
creator: Kilian Schwarz
date: 2007-04-26T04:39:04-00:00

Re: Meeting on Thursday, April 26, 2007
type: item
description: Dear all, because of the memory consumption of ALICE jobs: please contact also W. Schoen. He monitored the memory consumption on the batch farm machines with some tool of his. According to my memory we had a peak consumption of something like 4-5 GB during reconstruction, I believe, and an average memory consumption of around 2 GB. For sure our finding was, that with the peak memory consumption we could not run safely two jobs at the same time on a 8 GB RAM machine, assuming that they could reach their peak within the same time slot. I discussed that many times with Walter. Cheers, Kilian
creator: Kilian Schwarz
date: 2007-04-26T05:13:05-00:00