now my RAM runs around 30K...
How many modules have you got loaded and have you enabled HTTPS? Essentially, if you load everything, then your modules will allocate quite a lot of RAM at boot. My general approach is only to load the modules that my Lua apps are likely to use. I also keep my ESPs to a local control LAN / Wifi and use an RPi as a control bridge. I don't access the public internet (or talk directly to end user devices such as mobiles from my IoT devices. I usually have around 44 Kb free RAM at boot.
As a general check I run all my code through luac -l -l -o /dev/null file.lua and check the output; not so much the opcodes generated but scan for globals (_ENV references in Lua 5.3) and track my Upvalue use in my closures. Globals are bad news because they hang around even when you've finished with them. Locals are the cheapest type of variable storage both in terms of runtime and RAM footprint. I usually use outer scoping through Upvalues to make them accessible to inner functions; again a cheap and fast option. The thing about local declarations is that they are allocated on the stack so they only take up a Tvalue (the minimun storage quantum in the Lua runtime), or relocated to a special linked area if closed because an inner function is still live but the outer defining function has completed. All Lua magic that just works; and incidentally works really efficiently. Lua locals are garbage collected once they leave scope.
Another little trick is if a module contains any one-time initialisation, then wrap any sub functions within its scope and make it ephemeral as follows. Note that this only works if it is one-time. A second call will crater as the local variable referencing now holds nil. If this is compiled into LFS, then all of the code, constants and code metadata are in LFS. Yes it will use some RAM during execution, but this will all be returned to the heap on garbage collection after exiting its scope.
local function someInit() -- Upvalues: someInit and what other outer module locals are used
someInit = nil
-- other local and local functions
local function x() --[[ etc ]] end
-- ...
end
@TerryE Sorry, I had the repo set to private in case I published my password, which is still a good precaution, so I made a public one... https://github.com/poorandunlucky/lfs-public
sorry about that 😕
.gitexcludeto prevent this file from being added to the repo. However, remember that this will still leave these secrets in a form that can still be read from flash. There are ways to mitigate this but things can get quite complicated to do this properly.
log.luais pretty verbose for what it does uses RAM where there is little to be gained from doing so:module()andpackage.seeallare Lua 5.0 constructs which are deprecated in 5.1 and run inefficiently on NodeMCU. I am not even sure they work in Lua 5.3.- You shouldn't be printing errors -- that's just a good way to miss them in prod systems. Errors are just that and in Lua they should be thrown with an
error()statement. - In general this code would be fine for running on a real system with lots of RAM, but its not a good fit for a IoT device with ~40Kb RAM. OK, you want a
log(message,facility, level )function and the ability to configure the level from 'DEBUG' toNONEwith an option filename, but this IoT functionality doesn't need RAM arrays or this quite verbose logic. - for example the
strtolvl2()logic could be coded in a dozen lines, run faster and use no RAM arrays:level = level:upper() if ( level == 'DEBUG' ) then return 7 -- ... elseif level == 'EMERG' or level == 'EMERGENCY' then return 0 else error( 'Invalid error level specified: '..level) end - `lvl2str()2 is just the conjugate, but given that these seem to be private methods anyway so that the API can be sloppy over whether string or numeric log levels would be used, I am not sure if this code is needed.
I've got other suggestions, but this I am not sure here is the place to do it.
BTW, you could also code the str2lvl function something like the following. Perhaps, not the clearest code, but only a 26 instruction function that is fast and has low RAM use in an ESP8266 LFS context. OK, it will miscode error levels like "NOTE", but IMO it does the job. (Note that string.find(s,p,i,true) does a simple fast memory scan.)
local function str2lvl(s)
local vals = 'DEB\07INF\6NOT\5WAR\4ERR\3CRI\2ALE\1EME\0'
local i = vals:find(s:sub(1,3):upper(),1,true) or error('Invalid error level '..s)
return vals:sub(i+3,i+3):byte()
endOf course there are many ways of implementing this, but some take far less ESP8266 resources than others. All you need is a little lateral thinking in your approach.
Hello; just wanted to say thankyou to the hard-work put into this project; I've come back to use the esp8266 that have been lying around not being used for too long.
Very much enjoying using them. As a professional software engineer by day, I can see the effort that's gone into it :clap:
