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From Juho Mäkinen <juho.maki...@gmail.com>
Subject Re: Poor performance; PHP &amp; Thrift to blame
Date Mon, 23 Aug 2010 06:23:59 GMT
Beware that the native thrift php bindings has a bug which might
change provided argument types. Check out the bug report which I
filled:
https://issues.apache.org/jira/browse/THRIFT-796

 - Garo

On Fri, Aug 20, 2010 at 10:35 AM, sasha <sasha2048@gmail.com> wrote:
> Julian Simon <jsimon <at> jules.com.au> writes:
>
>>
>> Hi,
>>
>> I've been trying to benchmark Cassandra for our use case and have been
>> seeing poor performance on both writes and (extremely) poor
>> performance on reads.
>>
>> Using Cassandra 0.51 stable & thrift-0.2.0.
>>
>> It turns out all the CPU time is going to the PHP client process - the
>> JVM operating the Cassandra server isn't breaking much of a sweat.
>>
>> For reads the latency is often up to 1 second to fetch a row
>> containing ~2000 columns, or around 300ms to fetch a 500-column wide
>> row.  This is with get_slice(), and a predicate specifying the start &
>> finish range.
>>
>> Using cachegrind and inspecting the code inside the Thrift bindings
>> makes it pretty clear why the performance is so bad, particularly on
>> reads. The biggest culprit is the translation code which casts data
>> back and forth into binary representations for sending over the wire
>> to the Cassandra server.
>>
>> There seems to be some 32-bit specific code which iterates heavily
>> apparently due to a limitation in PHPs implementation of LONGs.
>>
>> However, testing on a 64-bit host doesn't yield any performance improvement.
>>
>> More surprisingly, if I compile and enable the PHP native thrift
>> bindings (following this guide
>> https://wiki.fourkitchens.com/display/PF/Using+Cassandra+with+PHP)
>> read performance actually degrades by another 50%.  I have verified
>> that the Thrift code is recognizing and using the native PHP functions
>> provided by the library.
>>
>> I've tested all of this on both 32-bit and 64-bit installations of
>> both PHP 5.1 & 5.2.  Results are the same in all cases.
>>
>> My environment is on vanilla CentOS 5.4 server installations inside
>> VMWare on a 4 core 64bit host with plenty of RAM and fast disks.
>>
>> Has anyone been able to produce decent performance with PHP &
>> Cassandra?  If so, how have you done it?
>>
>> Thanks,
>> Jules
>>
>>
>
>
> I had exactly the same problem: without native thrift bindings the performance
> was low and PHP used too much CPU. But when I compiled
> and enabled the native thrift bindings (following this guide https://
> wiki.fourkitchens.com/display/PF/Using+Cassandra+with+PHP), the performance
> became even lower, it degraded SEVERAL TIMES (although CPU usage decreased too).
>
> With the several random tries I discovered, that the buffer size matters. I
> mean the second and the third arguments for "new TBufferedTransport($socket, X,
> Y)". But the most surprising fact is that it matters much more when using
> native thrift bindings than when not using them.
>
> I.e.:
> - get_range_slices without native thrift bindings (either small or large buffer
> size): ~1sec.
> - get_range_slices with native thrift bindings and small buffer size (1024):
> ~5sec!
> - get_range_slices with native thrift bindings and large buffer size (40960):
> ~0.1sec.
>
> I don't know why!!
>
> P.S.: cassandra 0.6.3.
>
>
>

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