PATCH: Add DTrace probes

[Roy Lyseng]

Well, I hoped it would spur some more clever ideas...

I thought it could be useful if you have some problems with your 
application, and can use dtrace to track what operations are actually 
performed on one particular key.

But aggregations may probably be more interesting.

Roy

Paul van den Bogaard wrote:
> Mmm, I think that if copyinstr(arg1) == '1234..." that your trace output 
> will be rather dull :-)
> 
> --Paul
> 
> 
> On 7-mrt-2008, at 14:37, Roy Lyseng wrote:
> 
>> Another, slightly more advanced script is memcached-keytrace.d:
>>
>> :memcached::command-set,command-add,command-delete,command-get
>> /pid == $target && copyinstr(arg1) == "123456789"/
>> {
>>     trace(copyinstr(arg1));
>> }
>>
>> END
>> {
>> }
>>
>> This one will trace set, add, delete and get commands applied to one 
>> specific key:
>>
>> Invoke as:
>>
>> dtrace -s ~/memcached/dtrace/memcached-trace.d -p 24167
>>
>> Then run a telnet session:
>>
>> telnet system 11211
>> Trying 9.9.9.9...
>> Connected to system.
>> Escape character is '^]'.
>> abcdefghij
>> ERROR
>> set 123456789 0 0 10
>> abcdefghij
>> STORED
>> delete 123456789 0 0
>> DELETED
>> get 123456789 0 0 0
>> END
>>
>> And the dtrace script reports:
>>
>> CPU     ID                    FUNCTION:NAME
>>   1  54165       complete_nread:command-set   123456789
>>   0  54159 process_delete_command:command-delete   123456789
>>   1  54160  process_get_command:command-get   123456789
>>
>> Useful? Maybe...
>>
>> Roy
>> Dustin Sallings wrote:
>>>   For those of us who haven't truly unleashed the power of dtrace, 
>>> can you describe the kinds of things we can learn from this (perhaps 
>>> with scripts)?
>>> --Dustin Sallings (mobile)
>>> On Mar 6, 2008, at 4:48, Trond Norbye <Trond.Norbye at Sun.COM> wrote:
>>>>
>>>> On Mar 5, 2008, at 3:52 PM, Trond Norbye wrote:
>>>>
>>>>> The following patch adds a new configure-option (--enable-dtrace) 
>>>>> that adds DTrace probes to various parts of memcached.
>>>>>
>>>>> Please comment.
>>>>>
>>>>> Trond
>>>>
>>>> I discovered that I had some "leftovers" in this patch from before I 
>>>> fixed the comments regarding the large page support..
>>>>
>>>> The attached version is replacement for the original patch.
>>>>
>>>> Trond
>>>> <dtrace.patch.gz>
>>>>
> 
> --------------------------------------------------------------------------------------------- 
> 
> Paul van den Bogaard                               
> Paul.vandenBogaard at sun.com
> ISV-E  -- ISV Engineering, Opensource Engineering group
> 
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