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https://issues.apache.org/jira/browse/HBASE-1177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12718723#action_12718723
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Jim Kellerman commented on HBASE-1177:
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Tried running the read test backwards (reading 104 columns...6 columns). The
first few rows were slower, but the big blip still existed between 23...10
columns. Something is really goofy.
{code}
Read 1 row with 104 columns 100 times in 1170 ms
Read 1 row with 103 columns 100 times in 313 ms
Read 1 row with 102 columns 100 times in 820 ms
Read 1 row with 101 columns 100 times in 809 ms
Read 1 row with 100 columns 100 times in 403 ms
Read 1 row with 99 columns 100 times in 704 ms
Read 1 row with 98 columns 100 times in 317 ms
Read 1 row with 97 columns 100 times in 246 ms
Read 1 row with 96 columns 100 times in 169 ms
Read 1 row with 95 columns 100 times in 179 ms
...
Read 1 row with 24 columns 100 times in 65 ms
Read 1 row with 23 columns 100 times in 3999 ms
Read 1 row with 22 columns 100 times in 4000 ms
Read 1 row with 21 columns 100 times in 4000 ms
Read 1 row with 20 columns 100 times in 4000 ms
Read 1 row with 19 columns 100 times in 4000 ms
Read 1 row with 18 columns 100 times in 4000 ms
Read 1 row with 17 columns 100 times in 4000 ms
Read 1 row with 16 columns 100 times in 4000 ms
Read 1 row with 15 columns 100 times in 4000 ms
Read 1 row with 14 columns 100 times in 4000 ms
Read 1 row with 13 columns 100 times in 4000 ms
Read 1 row with 12 columns 100 times in 4000 ms
Read 1 row with 11 columns 100 times in 4000 ms
Read 1 row with 10 columns 100 times in 4000 ms
Read 1 row with 9 columns 100 times in 4000 ms
Read 1 row with 8 columns 100 times in 4000 ms
Read 1 row with 7 columns 100 times in 42 ms
{code}
Go figure...
> Delay when client is located on the same node as the regionserver
> -----------------------------------------------------------------
>
> Key: HBASE-1177
> URL: https://issues.apache.org/jira/browse/HBASE-1177
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.19.0
> Environment: Linux 2.6.25 x86_64
> Reporter: Jonathan Gray
> Assignee: Jim Kellerman
> Fix For: 0.20.0
>
> Attachments: Contribution of getClosest to getRow time.jpg,
> Contribution of next to getRow time.jpg, Contribution of seekTo to getClosest
> time.jpg, Elapsed time of RowResults.readFields.jpg, getRow + round-trip vs #
> columns.jpg, getRow times.jpg, ReadDelayTest.java, RowResults.readFields
> zoomed.jpg, screenshot-1.jpg, screenshot-2.jpg, screenshot-3.jpg,
> screenshot-4.jpg, zoom of columns vs round-trip blowup.jpg
>
>
> During testing of HBASE-80, we uncovered a strange 40ms delay for random
> reads. We ran a series of tests and found that it only happens when the
> client is on the same node as the RS and for a certain range of payloads (not
> specifically related to number of columns or size of them, only total
> payload). It appears to be precisely 40ms every time.
> Unsure if this is particular to our architecture, but it does happen on all
> nodes we've tried. Issue completely goes away with very large payloads or
> moving the client.
> Will post a test program tomorrow if anyone can test on a different
> architecture.
> Making a blocker for 0.20. Since this happens when you have an MR task
> running local to the RS, and this is what we try to do, might also consider
> making this a blocker for 0.19.1.
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