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Alessandro Presta commented on GIRAPH-301: ------------------------------------------ *few days > InputSplit Reservations are clumping, leaving many workers asleep while other > process too many splits and get overloaded. > ------------------------------------------------------------------------------------------------------------------------- > > Key: GIRAPH-301 > URL: https://issues.apache.org/jira/browse/GIRAPH-301 > Project: Giraph > Issue Type: Improvement > Components: bsp, graph, zookeeper > Affects Versions: 0.2.0 > Reporter: Eli Reisman > Assignee: Eli Reisman > Labels: patch > Fix For: 0.2.0 > > Attachments: GIRAPH-301-1.patch, GIRAPH-301-2.patch, > GIRAPH-301-3.patch, GIRAPH-301-4.patch, GIRAPH-301-5.patch, GIRAPH-301-6.patch > > > With recent additions to the codebase, users here have noticed many workers > are able to load input splits extremely quickly, and this has altered the > behavior of Giraph during INPUT_SUPERSTEP when using the current algorithm > for split reservations. A few workers process multiple splits (often > overwhelming Netty and getting GC errors as they attempt to offload too much > data too quick) while many (often most) of the others just sleep through the > superstep, never successfully participating at all. > Essentially, the current algo is: > 1. scan input split list, skipping nodes that are marked "Finsihed" > 2. grab the first unfinished node in the list (reserved or not) and check its > reserved status. > 3. if not reserved, attempt to reserve & return it if successful. > 4. if the first one you check is already taken, sleep for way too long and > only wake up if another worker finishes a split, then contend with that > worker for another split, while the majority of the split list might sit > idle, not actually checked or claimed by anyone yet. > This does not work. By making a few simple changes (and acknowledging that ZK > reads are cheap, only writes are not) this patch is able to get every worker > involved, and keep them in the game, ensuring that the INPUT_SUPERSTEP passes > quickly and painlessly, and without overwhelming Netty by spreading the > memory load the split readers bear more evenly. If the giraph.splitmb and -w > options are set correctly, behavior is now exactly as one would expect it to > be. > This also results in INPUT_SUPERSTEP passing more quickly, and survive the > INPUT_SUPERSTEP for a given data load on less Hadoop memory slots. > -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira