The Observation Deck

Views on software from Bryan Cantrill's deck chair

Thursday August 04, 2005

DTrace and PHP Tonight during our OpenSolaris BOF at OSCON, PHP core developer Wez Furlong was busy adding a DTrace provider to PHP. After a little bit of work (and a little bit of debugging), we got it working -- and damn is it cool. Wez implemented it as a shared object, which may then be loaded via an explicit extension directive in php.ini. Once loaded, two probes show up: function-entry and function-return. These probes have as their arguments a pointer to the function name, a pointer to the file name, and a line number. This allows one to, for example, get a count of all PHP functions being called: # dtrace -n function-entry'{@[copyinstr(arg0)] = count()}' Or you can aggregate on file name and quantize by line number: # dtrace -n function-entry'{@[copyinstr(arg1)] = lquantize(arg2, 0, 5000)}' Or you can determine the amount of wall time taken by a given PHP function: # dtrace -n function-entry'/copyinstr(arg0) == "myfunc"/{self->ts = timestamp}' -n function-return'/self->ts/{@ = avg(timestamp - self->ts); self->ts = 0)}' And because it's DTrace, this can all be done on a production box -- and without regard to the number of PHP processes. (So if you have 200 Apache processes handling PHP, the above invocations would aggregate across them.) When I get back, I'll download Wez's provider and post some more comprehensive examples. In the meantime, if you're a PHP developer at OSCON, stop Wez if you see him and ask him to give you a demo -- it's the kind of thing that needs to be seen to be appreciated... Finally, if you're interested in adding your own DTrace provider to the application, language or system that you care about, be sure to check out my presentation on DTrace tomorrow at 4:30 in Portland room 255. (Hopefully this time I won't be tortured by memories of being mindfucked by Inside UFO 54-40.) (2005-08-04 03:25:35.0/2005-08-04 02:51:37.0) Permalink Comments [15]

# pear install dtrace
# echo "extension=dtrace.so" >> $prefix/lib/php.ini

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