From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp61.i.mail.ru (smtp61.i.mail.ru [217.69.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dev.tarantool.org (Postfix) with ESMTPS id D32AD445320 for ; Thu, 9 Jul 2020 17:02:21 +0300 (MSK) References: <20200629121118.21596-1-arkholga@tarantool.org> <20200701213441.GD5559@tarantool.org> <20200709010828.nlfq6sbavluwu6wf@tkn_work_nb> From: Olga Arkhangelskaia Message-ID: <45ba81c4-751b-1371-acfb-26279cc85696@tarantool.org> Date: Thu, 9 Jul 2020 17:02:20 +0300 MIME-Version: 1.0 In-Reply-To: <20200709010828.nlfq6sbavluwu6wf@tkn_work_nb> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Content-Language: en-GB Subject: Re: [Tarantool-patches] [PATCH 0/1] fix box.info:memory() List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Turenko , Igor Munkin Cc: tarantool-patches@dev.tarantool.org 09.07.2020 4:08, Alexander Turenko пишет: >>> There are two options to get rid if extra box.info table: >>> 1. Create new table in the beginning of the function(eg. box.info.gc). >>> Every time box.info.memory is called it will generate new table with the fresh >>> info. >>> 2. The second way is to ignore box.info argument on the stack and fill >>> directly box.info.memory table, that was passed as an argument. >>> >>> I have implemented the first approach because there is box.info.gc works >>> the same way and we only need to add one line of code. >>> However, I do not know why it was done in such a way on the first place. >>> So if you have pros for the second options, please share with me. >> I have no idea why it is implemented in such complex way, maybe Sasha >> does? Why box.info.memory yields an empty "callable" table on each >> lookup? Why it can't just return a function to be called or a table with >> memory metrics as a result of the lookup? Unfortunately the latter >> approach breaks the backward compatibility but the first one can save >> some time on short-term objects creation (I guess no one checks >> box.info.memory type). Thoughts? Please also consider the comments I >> left for the patch itself. > I don't see a reason. The history of src/box/lua/info.c changes shows > that this way was initially implemented for box.info.phia() (which was > renamed later to box.info.vinyl()). Then box.info.memory(), > box.info.gc() and box.info.sql() were added in the same way. > box.info.phia() was moved from box.phia(). > > I agree with you. We should define a case to estimate impact of > replacing a table + metamethod with a function. Not even to make a > decision whether it worth to change, but to imagine the situation at > whole. > > I would consider metrics collection case using tarantool/metrics every > minute when default metrics are enabled. I guess it'll call > box.info.vinyl(), box.info.memory() and box.info.gc() once for each > metrics collection. So the proposed change will safe 3 extra short-term > object creations per minute. > > I don't see a case when those functions should be called more often and > become a part of hot path. So I would say that reducing of GC object > allocations here does not look worthful for me considering possible > impact of subtle differences (like serialization of `box.info` or other > differences we can miss) that may fail some scripts or tools. > >>> [1] https://www.lua.org/manual/5.1/manual.html#2.8 >>> >>> @Changelog: >>> To retrieve information about memory usage box.info:memory() can be used. > If you are a user, which read release notes and doesn't aware of the > problem (and don't remember whether box.info.memory() or > box.info:memory() is suggested by the documentation), then it is hard to > understand what was changed. I would explicitly mention > `box.info.memory()` variant of the call: this way the idea of the change > would be more clear. @Changelog: box.info:memory() gives the same result as box.info.memory()(gh-4688). > > BTW, don't forget to include an issue number (see examples in existing > release notes on GitHub).