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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: multiget_slice
Date Thu, 14 Jan 2010 17:22:32 GMT
it sounds like you just don't have enough ram for the OS to cache your
"hot" data set so you are getting killed on disk seeks.  iostat -x 5
(for example) during load should verify this.

On Thu, Jan 14, 2010 at 11:19 AM, Suhail Doshi <digitalwarfare@gmail.com> wrote:
> Looking at my data directory: 14 G. Just Index.db based files: 4.5 G.
>
> Yes only one node so far.
>
> vmstat -n 1 -S m
> procs -----------memory---------- ---swap-- -----io---- -system--
> ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy
id
> wa
>  0  0     22    585     32   2557    0    0    71    31    5    5
 1  0 94
>  3
>
> On Thu, Jan 14, 2010 at 10:11 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>
>> how much data do you have on disk?  (only on enode?)  how large are
>> the columns you are reading?  how much ram does vmstat say is being
>> used for cache?
>>
>> On Thu, Jan 14, 2010 at 11:06 AM, Suhail Doshi <digitalwarfare@gmail.com>
>> wrote:
>> > Right now it's ~5-10 keys, with 5 columns per key.
>> >
>> > Later it will be 64 keys (max) with 200 columns per key worst case.
>> >
>> > Suhail
>> >
>> > On Thu, Jan 14, 2010 at 9:45 AM, Jonathan Ellis <jbellis@gmail.com>
>> wrote:
>> >
>> >> how many keys are you fetching?  how many columns for each key?
>> >>
>> >> On Thu, Jan 14, 2010 at 1:49 AM, Suhail Doshi <suhail@mixpanel.com>
>> wrote:
>> >> > I've been seeing multiget_slice take an extremely long time:
>> >> >
>> >> > 2010-01-14 07:44:00,513 INFO ------------------ Cassandra, delay:
>> >> > 3.64020800591 -----------------------
>> >> > 2010-01-14 07:44:00,513 INFO method: multiget_slice
>> >> > 2010-01-14 07:44:00,513 INFO {'keys':
>> >> >
>> >>
>> [u'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:a93ec971e867b23664d990336ce481e0:7516fd43adaa5e0b8a65a672c39845d2',
>> >> >
>> >>
>> u'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:fe33779b0db3213f7e354c8e22ad9939:4df200d45716195e86c09a94a54a0c7a',
>> >> >
>> >>
>> u'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:71860c77c6745379b0d44304d66b6a13:e37f0136aa3ffaf149b351f6a4c948e9',
>> >> >
>> >>
>> u'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:1240f61999709d41292f759e500ad5be:69691c7bdcc3ce6d5d8a1361f22d04ac',
>> >> >
>> >>
>> u'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:a6d5b5c3d715b79b59caf7aed18301ac:b53b3a3d6ab90ce0268229151c9bde11'],
>> >> > 'column_parent': ColumnParent(column_family='DistinctIndex',
>> >> > super_column=None), 'predicate': SlicePredicate(column_names=None,
>> >> > slice_range=SliceRange(count=14000, start='date_2009-07-01',
>> >> reversed=False,
>> >> > finish='date_2010-01-14'))}
>> >> >
>> >> > 2010-01-14 07:44:00,513 INFO result:
>> >> >
>> >> > 2010-01-14 07:44:00,513 INFO
>> >> >
>> >>
>> {'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:fe33779b0db3213f7e354c8e22ad9939:4df200d45716195e86c09a94a54a0c7a':
>> >> > [ColumnOrSuperColumn(column=Column(timestamp=1263231323,
>> >> > name='date_2010-01-11', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263333256,
>> >> > name='date_2010-01-12', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263418556,
>> >> > name='date_2010-01-13', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263451804,
>> >> > name='date_2010-01-14', value='1'), super_column=None)],
>> >> >
>> >>
>> 'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:71860c77c6745379b0d44304d66b6a13:e37f0136aa3ffaf149b351f6a4c948e9':
>> >> > [ColumnOrSuperColumn(column=Column(timestamp=1263231323,
>> >> > name='date_2010-01-11', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263333256,
>> >> > name='date_2010-01-12', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263418556,
>> >> > name='date_2010-01-13', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263451804,
>> >> > name='date_2010-01-14', value='1'), super_column=None)],
>> >> >
>> >>
>> 'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:a6d5b5c3d715b79b59caf7aed18301ac:b53b3a3d6ab90ce0268229151c9bde11':
>> >> > [ColumnOrSuperColumn(column=Column(timestamp=1263333256,
>> >> > name='date_2010-01-12', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263418556,
>> >> > name='date_2010-01-13', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263451804,
>> >> > name='date_2010-01-14', value='1'), super_column=None)],
>> >> >
>> >>
>> 'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:a93ec971e867b23664d990336ce481e0:7516fd43adaa5e0b8a65a672c39845d2':
>> >> > [ColumnOrSuperColumn(column=Column(timestamp=1263231323,
>> >> > name='date_2010-01-11', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263333256,
>> >> > name='date_2010-01-12', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263418556,
>> >> > name='date_2010-01-13', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263451804,
>> >> > name='date_2010-01-14', value='1'), super_column=None)],
>> >> >
>> >>
>> 'property:1558:1f0351b7f85b4aa070548e5fd5e08ddf:fce1eab4411d5df240d93ff334f15385:1240f61999709d41292f759e500ad5be:69691c7bdcc3ce6d5d8a1361f22d04ac':
>> >> > [ColumnOrSuperColumn(column=Column(timestamp=1263231323,
>> >> > name='date_2010-01-11', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263333256,
>> >> > name='date_2010-01-12', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263418556,
>> >> > name='date_2010-01-13', value='1'), super_column=None),
>> >> > ColumnOrSuperColumn(column=Column(timestamp=1263451804,
>> >> > name='date_2010-01-14', value='1'), super_column=None)]}
>> >> >
>> >> >
>> >> > The delay is the time at which it took to run the query and then
>> return a
>> >> > result. The box has 4GB of RAM and the *JVM_MAX_MEM (-Xmx) is set at
>> 3G*.
>> >> If
>> >> > you're curious how I am running it:
>> >> >
>> >> > /usr/bin/jsvc -home /usr/lib/jvm/java-6-openjdk/jre -pidfile
>> >> > /var/run/cassandra.pid -errfile &1 -outfile
>> /var/log/cassandra/output.log
>> >> > -cp
>> >> >
>> >>
>> /usr/share/cassandra/antlr-3.1.3.jar:/usr/share/cassandra/apache-cassandra-incubating-0.5.0-rc1.jar:/usr/share/cassandra/apache-cassandra-incubating.jar:/usr/share/cassandra/clhm-production.jar:/usr/share/cassandra/commons-cli-1.1.jar:/usr/share/cassandra/commons-collections-3.2.1.jar:/usr/share/cassandra/commons-lang-2.4.jar:/usr/share/cassandra/google-collect-1.0-rc1.jar:/usr/share/cassandra/high-scale-lib.jar:/usr/share/cassandra/jline-0.9.94.jar:/usr/share/cassandra/json_simple-1.1.jar:/usr/share/cassandra/junit-4.6.jar:/usr/share/cassandra/libthrift-r894924.jar:/usr/share/cassandra/log4j-1.2.15.jar:/usr/share/cassandra/slf4j-api-1.5.8.jar:/usr/share/cassandra/slf4j-log4j12-1.5.8.jar:/etc/cassandra:/usr/share/java/commons-daemon.jar
>> >> > -Xmx3G -Xms128M -Dcassandra -Dstorage-config=/etc/cassandra
>> >> > -Dcom.sun.management.jmxremote.port=8080
>> >> > -Dcom.sun.management.jmxremote.ssl=false
>> >> > -Dcom.sun.management.jmxremote.authenticate=false
>> >> > org.apache.cassandra.service.CassandraDaemon
>> >> >
>> >> > I am running version* 0.5.0rc2*.
>> >> >
>> >> > Does anyone know what the bottleneck might be and how reads using
>> >> > multiget_slice can be sped up? When I look at the memory used, it's
>> only
>> >> > about 1700 MB used. The box is not excessively swapping, running
>> >> > iostat--everything seemed pretty okay.
>> >> >
>> >> > Suhail
>> >> >
>> >>
>> >
>> >
>> >
>> > --
>> > http://mixpanel.com
>> > Blog: http://blog.mixpanel.com
>> >
>>
>
>
>
> --
> http://mixpanel.com
> Blog: http://blog.mixpanel.com
>

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