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From Adam Kocoloski <kocol...@apache.org>
Subject Re: worst performance in 1.1.x (compared to 1.0.x)
Date Mon, 13 Dec 2010 03:02:19 GMT
I tried R14B01, the custom small_doc.json, and lowering schedulers_online to 1, but the writers
continue to starve.  Trunk (4137a8e) does not starve the writers, almost certainly due to
your updater_fd patch.  Comparing trunk and the mochiweb upgrade commit I get

http://graphs.mikeal.couchone.com/#/graph/df0f79455c9c600f66d1ce42ea018d7e

I think it's still important that you observe a performance regression with the introduction
of that patch, but  something else in our respective setups clearly has a much greater effect
on the results.  Regards,

Adam

On Dec 12, 2010, at 8:42 PM, Adam Kocoloski wrote:

> Hi Filipe, I cannot reproduce those results at all, though I didn't try loading the custom
small_doc.json.  If I use 200 readers and 100 writers the writers are completely starved and
I get e.g.
> 
> http://graphs.mikeal.couchone.com/#/graph/df0f79455c9c600f66d1ce42ea016e07
> 
> I need to lower the readers down to ~20 to keep the write throughput reasonable.  I'm
running R13B04 on a dual-core OS X 10.6 MacBook.  I'll try a few more things including the
custom doc and R14B01, but do you have suggestions for why these results might be so dramatically
different?
> 
> Adam
> 
> On Dec 12, 2010, at 7:17 AM, Filipe David Manana wrote:
> 
>> Hi,
>> 
>> While running a relaximation test to compare read/write performance
>> between 1.1.x and 1.0.x, I found out that 1.1.x has worst performance
>> 
>> It seems the cause is related to the new Mochiweb version introduced
>> in commit 4b0948ddb3a428f8a5330e05745b2fbd4ccf9375 -
>> https://github.com/apache/couchdb/commit/4b0948ddb3a428f8a5330e05745b2fbd4ccf9375
>> 
>> Comparing the performance of this revision with the previous one
>> (cd214b23e8129868d4a7020ddafd55a16e496652), I get the following
>> results:
>> 
>> http://graphs.mikeal.couchone.com/#/graph/df0f79455c9c600f66d1ce42ea0125e5
>> 
>> Both read and write performance are worse for
>> 4b0948ddb3a428f8a5330e05745b2fbd4ccf9375.
>> 
>> The cause could be the configuration we pass to Mochiweb in
>> couch_httpd. The new Mochiweb sets the nodelay option to false by
>> default and it uses now several acceptor processes (16 by default).
>> However even with the following small patch I still get about the same
>> disappointing results:
>> 
>> diff --git a/src/couchdb/couch_httpd.erl b/src/couchdb/couch_httpd.erl
>> index 23ff7f9..e93c7e7 100644
>> --- a/src/couchdb/couch_httpd.erl
>> +++ b/src/couchdb/couch_httpd.erl
>> @@ -97,7 +97,9 @@ start_link(Name, Options) ->
>>    {ok, Pid} = case mochiweb_http:start(Options ++ [
>>        {loop, Loop},
>>        {name, Name},
>> -        {ip, BindAddress}
>> +        {ip, BindAddress},
>> +        {nodelay, true},
>> +        {acceptor_pool_size, 32}
>>    ]) of
>>    {ok, MochiPid} -> {ok, MochiPid};
>>    {error, Reason} ->
>> 
>> 
>> (Also tried higher values for acceptor_pool_size, which doesn't help)
>> 
>> The test was run like this:
>> 
>> $ node tests/compare_write_and_read.js --wclients 100 --rclients 200 \
>> -name1 new_4b0948ddb3a428f8a5330e05745b2fbd4ccf9375 -name2
>> old_cd214b23e8129868d4a7020ddafd55a16e496652 \
>> -url1 http://localhost:5984/ -url2 http://localhost:5985/ \
>> --duration 120
>> 
>> With the following document template (file
>> relaximation/common/small_doc.json):
>> http://friendpaste.com/7GKUEg0SZHmOf0g7Dh5IWC
>> 
>> Can anyone confirm these results?
>> If confirmed, I would say this is a blocker for 1.1.0.
>> 
>> thanks
>> 
>> 
>> -- 
>> Filipe David Manana,
>> fdmanana@gmail.com, fdmanana@apache.org
>> 
>> "Reasonable men adapt themselves to the world.
>> Unreasonable men adapt the world to themselves.
>> That's why all progress depends on unreasonable men."
> 


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