Re: Use "ropes" for string concatenation

Hey: On Tue, Mar 24, 2015 at 2:04 PM, Pierre Joye <pierre.php@gmail.com> wrote: > On Tue, Mar 24, 2015 at 1:01 PM, Xinchen Hui <xinchen.h@zend.com> wrote: >> Hey: >> >> On Tue, Mar 24, 2015 at 1:54 PM, Pierre Joye <pierre.php@gmail.com> wrote: >>> On Tue, Mar 24, 2015 at 12:35 PM, Xinchen Hui <xinchen.h@zend.com> wrote: >>>> Hey: >>>> >>>> On Tue, Mar 24, 2015 at 1:31 PM, Pierre Joye <pierre.php@gmail.com> wrote: >>>>> hi! >>>>> >>>>> On Tue, Mar 24, 2015 at 5:41 AM, Dmitry Stogov <dmitry@zend.com> wrote: >>>>>> Hi, >>>>>> >>>>>> Recently, Xinchen and me worked on optimization that eliminates useless >>>>>> reallocations and copying during string concatenation (ZEND_ADD_STRING and >>>>>> family + ZEND_CONCAT). >>>>>> >>>>>> The idea comes from ropes, but adopted especially for our needs. >>>>>> Rope is popular data structure in languages with immutable strings. >>>>>> â< >>>>>> ¯å_°m/|—†ñhttp://en.wikipedia.org/wiki/Rope_%28data_structure%29 >>>>>> >>>>>> We don't try to use ropes everywhere in the engine (at least it's >>>>>> too later >>>>>> for 7.0), only for concatenation. >>>>>> >>>>>> The first branch uses ropes only instead of ZEND_ADD_STRING and family. >>>>>> This must be safe. The only problem is possible memory leaks on exception >>>>>> (but we already have this problem anyway). The simplest way to understand >>>>>> the patch - read code for new opcodes in zend_vm_def.h. >>>>>> >>>>>> https://github.com/php/php-src/pull/1194/files•]† ê3!J >>>>>> ;kË,BÒ >>>>>> >>>>>> The second branch in addition uses ropes for series of ZEND_CONCAT. It >>>>>> disables calls to do_operation(ZEND_CONCAT) handler of custom internal >>>>>> classes. >>>>>> >>>>>> >>>>>> https://github.com/php/php-src/pull/1195/files >>>>>> >>>>>> Both make slight speed improvement (first +0.3%, second +0.6% on wordpress >>>>>> home page). >>>>>> >>>>>> We don't currently use ability to override CONCAT behavior in internal >>>>>> classes, and I'm not sure if it may be useful at all. (For example Lua >>>>>> doesn't provide concat meta-method). May be remove it? >>>>>> >>>>>> Thoughts and comments are welcome. >>>>> >>>>> Great work! :) >>>>> >>>>> Do you expect similar gain for other ops? >>>>> >>>>> I wonder if it would not be better to target 7.1 for that, adding it >>>>> for other string operations, in one go. Most of the current patch is >>>>> self contained, it adds quite some complexity to the engine for these >>>>> operations only and it is not a small change at this stage (post >>>>> features freeze). It sounds like a possible maintenance pain. Taking >>>> Actually, it's not. >>>> >>>> previously we have ADD_STRING/CHAR/VAR and CONCAT >>>> >>>> the 2nd branch cleanup these, and now we only deal with one type concat_list. :) >>> >>> Right, it simplifies part of the existing implementation and add some >>> complexities to other. It only adds this OP and keep other with the >>> "old" implementation, that's actually the only part where I am not >>> totally convinced. It may make sense to do it all at once, if that's >>> the long term plan, easier to maintain. >>> >>> But if we do prefer to add this now, then the sooner the better, it >>> may have some hard to catch bugs. Now, we have one issue, we cannot >>> have a RFC (deadline behind us) and this is still a rather big change >>> :/ >> from user land. this won't change anything.. > > Nothing to do with userland or not but code stabilization In that case, yeah. you might be right. but from my opinion, simpler always means easier for maintaining.... anyway, I hope this could be merged to 7.0(the second branch) :) thanks > >> and regarding to the object overriden concat..... >> >> I doubt it is not used at all :) > > -- > Pierre > > @pierrejoye | http://www.libgd.org -- Xinchen Hui @Laruence http://www.laruence.com/