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From Ivan Georgiev <>
Subject 0.7.2 slow memtables flushing
Date Sat, 19 Feb 2011 14:16:43 GMT

I am testing 0.7.2 on a Windows 2003 x64 system(one node) and I am 
having the following problem.
My insertion speed is relatively slow, so the memtables do not get full 
and the actual flushing is triggered by memtable_flush_after_mins, this 
happens on the hour mark. My problem with 0.7.2 is that when that 
happens, the cpu spikes to 25% overall usage (x4 Xeon) and the operation 
takes anywhere from 2 to 4 minutes, leaving the node not responding 
during that time. This has forced to me to increase the rpc timeout 
option to beyond what i feel comfortable with.
I have run multiple tests with 0.7.0 and 0.7.2 with the same dataset and 
the results are consistent. During the same operation 0.7.0 takes about 
10 seconds to complete vs. 2 to 4 minutes for 0.7.2. I am attaching a 
log with the timestamps from one such flushing of 0.7.2. Please let me 
know if there is anything i can do to speed up and get results similar 
to 0.7.0.


This is the log of the operations which took most time during the flush 
operation. Using 0.7.0, with the same number of operations the flushing 
takes less than 10 seconds.

INFO 01:36:44,906 Enqueuing flush of 
Memtable-ArchiveFiles.6f776e65724944@1225856921(1619949 bytes, 34467 
INFO 01:37:47,375 Completed flushing 
C:\Storage\data\Storage\ArchiveFiles.68617368-f-3-Data.db (5549187 bytes)
INFO 01:37:47,375 Writing 
Memtable-ArchiveFiles.6e616d65@978152661(1619949 bytes, 34467 operations)
INFO 01:37:47,375 Enqueuing flush of 
bytes, 34467 operations)
INFO 01:38:51,343 Completed flushing 
C:\Storage\data\Storage\ArchiveFiles.6e616d65-f-3-Data.db (3820265 bytes)
INFO 01:38:51,343 Writing 
Memtable-ArchiveFiles.6f776e65724944@1225856921(1619949 bytes, 34467 

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