I am not sure - my recollection is that the 1.6.x code capped the number of threads requested at 1 per tablet (covered by the requested ranges), not 1 per tablet server.
-----Original Message----- From: Josh Elser [mailto:[email protected]] Sent: Monday, September 12, 2016 10:58 AM To: [email protected] Subject: Re: Accumulo Seek performance Good call. I kind of forgot about BatchScanner threads and trying to factor those in :). I guess doing one thread in the BatchScanners would be more accurate. Although, I only had one TServer, so I don't *think* there would be any difference. I don't believe we have concurrent requests from one BatchScanner to one TServer. Dylan Hutchison wrote: > Nice setup Josh. Thank you for putting together the tests. A few > questions: > > The serial scanner implementation uses 6 threads: one for each thread in > the thread pool. > The batch scanner implementation uses 60 threads: 10 for each thread in > the thread pool, since the BatchScanner was configured with 10 threads > and there are 10 (9?) tablets. > > Isn't 60 threads of communication naturally inefficient? I wonder if we > would see the same performance if we set each BatchScanner to use 1 or 2 > threads. > > Maybe this would motivate a /MultiTableBatchScanner/, which maintains a > fixed number of threads across any number of concurrent scans, possibly > to the same table. > > > On Sat, Sep 10, 2016 at 3:01 PM, Josh Elser <[email protected] > <mailto:[email protected]>> wrote: > > Sven, et al: > > So, it would appear that I have been able to reproduce this one > (better late than never, I guess...). tl;dr Serially using Scanners > to do point lookups instead of a BatchScanner is ~20x faster. This > sounds like a pretty serious performance issue to me. > > Here's a general outline for what I did. > > * Accumulo 1.8.0 > * Created a table with 1M rows, each row with 10 columns using YCSB > (workloada) > * Split the table into 9 tablets > * Computed the set of all rows in the table > > For a number of iterations: > * Shuffle this set of rows > * Choose the first N rows > * Construct an equivalent set of Ranges from the set of Rows, > choosing a random column (0-9) > * Partition the N rows into X collections > * Submit X tasks to query one partition of the N rows (to a thread > pool with X fixed threads) > > I have two implementations of these tasks. One, where all ranges in > a partition are executed via one BatchWriter. A second where each > range is executed in serial using a Scanner. The numbers speak for > themselves. > > ** BatchScanners ** > 2016-09-10 17:51:38,811 [joshelser.YcsbBatchScanner] INFO : Shuffled > all rows > 2016-09-10 17:51:38,843 [joshelser.YcsbBatchScanner] INFO : All > ranges calculated: 3000 ranges found > 2016-09-10 17:51:38,846 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:52:19,025 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 40178 ms > 2016-09-10 17:52:19,025 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:53:01,321 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 42296 ms > 2016-09-10 17:53:01,321 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:53:47,414 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 46094 ms > 2016-09-10 17:53:47,415 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:54:35,118 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 47704 ms > 2016-09-10 17:54:35,119 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:55:24,339 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 49221 ms > > ** Scanners ** > 2016-09-10 17:57:23,867 [joshelser.YcsbBatchScanner] INFO : Shuffled > all rows > 2016-09-10 17:57:23,898 [joshelser.YcsbBatchScanner] INFO : All > ranges calculated: 3000 ranges found > 2016-09-10 17:57:23,903 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:57:26,738 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 2833 ms > 2016-09-10 17:57:26,738 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:57:29,275 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 2536 ms > 2016-09-10 17:57:29,275 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:57:31,425 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 2150 ms > 2016-09-10 17:57:31,425 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:57:33,487 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 2061 ms > 2016-09-10 17:57:33,487 [joshelser.YcsbBatchScanner] INFO : > Executing 6 range partitions using a pool of 6 threads > 2016-09-10 17:57:35,628 [joshelser.YcsbBatchScanner] INFO : Queries > executed in 2140 ms > > Query code is available > https://github.com/joshelser/accumulo-range-binning > <https://github.com/joshelser/accumulo-range-binning> > > > Sven Hodapp wrote: > > Hi Keith, > > I've tried it with 1, 2 or 10 threads. Unfortunately there where > no amazing differences. > Maybe it's a problem with the table structure? For example it > may happen that one row id (e.g. a sentence) has several > thousand column families. Can this affect the seek performance? > > So for my initial example it has about 3000 row ids to seek, > which will return about 500k entries. If I filter for specific > column families (e.g. a document without annotations) it will > return about 5k entries, but the seek time will only be halved. > Are there to much column families to seek it fast? > > Thanks! > > Regards, > Sven > >
