On Fri, Dec 6, 2013 at 3:39 PM, Haribabu kommi
> On 06 December 2013 12:29 Amit Kapila wrote:
>> >> Note -
>> >> a. Performance is data is taken on my laptop, needs to be tested on
>> >> some better m/c b. Attached Patch is just a prototype of chunkwise
>> >> concept, code needs to be improved and decode
>> >> handling/test is pending.
>> > I ran the performance test on linux machine and attached the results
>> in the mail.
> I ran the performance test on above patches including another patch which
> Does snappy hash instead of normal hash in LZ algorithm. The performance
> Readings and patch with snappy hash not including new data in compression
> are attached in the mail.
Thanks for taking the data.
> The chunk wise approach is giving good performance in most of the scenarios.
Agreed, summarization of data for LZ/Chunkwise encoding especially for
non-compressible (hundred tiny fields, all changed/half changed) or less
compressible data (hundred tiny fields, half nulled) w.r.t CPU
usage is as below:
a. For hard disk, there is an overhead of 7~16% with LZ delta encoding
and there is an overhead of 5~8% with Chunk wise encoding.
b. For Tempfs (which means operate on RAM as disk), there is an
overhead of 19~26%
with LZ delta encoding and there is an overhead of 9~18% with
Chunk wise encoding.
There might be some variation of data (in your last mail the overhead
for chunkwise method for Tempfs was < 12%),
but in general the data suggests that chunk wise encoding has less
overhead than LZ encoding for non-compressible data
and for others it is better or equal.
Now, I think we have below options for this patch:
a. If the performance overhead for worst case is acceptable (we can
try to reduce some more, but don't think it will be something
then this can be done without any flag/option.
b. Have it with table level option to enable/disable WAL compression
c. Drop this patch, as for worst cases there is some performance overhead.
d. Go back and work more on it, if there is any further suggestions
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