The Speed of memcached

[Peter Alberer]

hurra, i found the problem. the socket was set to line buffering mode, 
after disabling that, the set operation is even faster than the get 
operation :)

thanks for the hints, peter

>Yes, you'll want to use TCP_NODELAY, disabling the Nagel algorithm.
>
>Otherwise you can cork/uncork (push/nopush on BSD) which immediately
>sends, but makes little sense in such a protocol as memcached without lots
>of data.
>
>Or I believe (?) you can just send(), which never does Nagel, at least on
>Linux, which is iirc why the Perl client doesn't have NODELAY in it.
>
>- Brad
>
>
>
>On Wed, 12 Oct 2005, Peter Alberer wrote:
>
>  
>
>>hm, no i cannot set that option from tcl for the socket as far as i know
>>:(
>>do you mean i should try to use it or not?
>> i have not seen that perl or phyton clients use TCP_NODELAY...
>>
>>    
>>
>>>If you rolled your own client, are you doing TCP_NODELAY?  That tends to
>>>be the first thing to bite people.
>>>
>>>
>>>On Wed, 12 Oct 2005, Peter Alberer wrote:
>>>
>>>
>>>
>>>      
>>>
>>>>Hi there,
>>>>
>>>>i have created a simple tcl-based client api to memcached for use in the
>>>>aolserver webserver. after the completion of the client api, my first
>>>>tests showed
>>>>that the memcached server is quite slow when saving values, compared to
>>>>my database (postgresql 8.0). i would like to mention, that i only open
>>>>the communication sockets once for all the
>>>>operations and cache it in the api.
>>>>
>>>>i created a test-loop that saves 100 different keys (test1-100) with the
>>>>same value (value length is about 1000 characters) to 2 different
>>>>memcached servers (50 each),
>>>>rereads all of the values and deletes all of them afterwards. (no multi
>>>>get, just 100 single get commands)
>>>>
>>>>Here are the results measured in ms:
>>>>
>>>>Memcache SET: Processed 100 items in 4060 ms
>>>>
>>>>Memcache GET: Processed 100 items in 438 ms
>>>>
>>>>Memcache DELETE: Processed 100 items in 82 ms
>>>>
>>>>The set command is quite slow, compared to the get and delete command.
>>>>are the numbers i am getting here reasonable? interestingly,
>>>>the VERY FIRST set command completes in 0-1 ms, but ALL of the
>>>>subsequent ones take 40-41ms. this is something i can even see when i
>>>>manually
>>>>set keys via telnet. the first set command returns STORED immediately,
>>>>but after that a very small delay is visible for every set command.
>>>>changing the length of the value
>>>>does not  affect the 40ms for storing the value, just the get operation
>>>>gets faster.
>>>>
>>>>have others measured the performance of the different memcached operations?
>>>>
>>>>i would be very glad to hear about your observations!
>>>>
>>>>TIA, peter
>>>>
>>>>ps: the system where the memcached daemon is running is a power5-redhat
>>>>AS4 server. kernel=2.6.9-11.EL
>>>>
>>>>
>>>>
>>>>
>>>>        
>>>>
>>    
>>