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- Subject: Re: Pre-emptive round robin scheduler around Lua VM
- From: l m <ml@...>
- Date: Tue, 1 Apr 2014 14:07:49 +0200
> Please can you share the example that would not work. The above example as you mentioned seems to work fine.
if I use my lua example on your code http://codepad.org/JEj381KW the
coroutine writing B is not continued nor even resumed
On 4/1/14, Milind Gupta <milind.gupta@gmail.com> wrote:
> Hi,
> Please can you share the example that would not work. The above example
> as you mentioned seems to work fine.
>
> Milind
>
>
>
>
> On Tue, Apr 1, 2014 at 4:13 AM, l m <ml@gizal.org> wrote:
>
>> hi,
>>
>>
>> it would not work for coroutines
>>
>> if there is more than one level of coroutine, i don't see a simple
>> solution
>>
>> with only one this seems to work ( with the issue that hook count is
>> not global ) :
>>
>> #include <lua.h>
>> #include <lauxlib.h>
>> #include "src/lstate.h"
>>
>> lua_State* resume_thread;
>> int resume_main;
>>
>> void hookFunc(lua_State *L, lua_Debug *ar) {
>> lua_State* M = L->l_G->mainthread;
>> if(L != M) {
>> if(resume_thread == M)
>> resume_thread = L;
>> M->hookcount = 1;
>> }
>> resume_main = 0;
>> lua_yield(L, 0);
>> }
>>
>> int main() {
>> lua_State *L1, *L2, *N1, *N2;
>>
>> L1 = luaL_newstate();
>> L2 = luaL_newstate();
>>
>> luaL_openlibs(L1);
>> luaL_openlibs(L2);
>>
>> lua_sethook(L1, hookFunc, LUA_MASKCOUNT, 500);
>> lua_sethook(L2, hookFunc, LUA_MASKCOUNT, 500);
>>
>> luaL_loadstring(L1, "function co() while true do for i=1,100 do
>> print('B') end coroutine.yield() end end"
>> " c = coroutine.create(co) coroutine.resume(c)"
>> " while true do for i=1,70 do print('A') end
>> coroutine.resume(c) end");
>> luaL_loadstring(L2, "while true do print('C') end");
>>
>> N1 = L1;
>> N2 = L2;
>>
>> for(;;)
>> {
>> resume_main = 1;
>> resume_thread = L1;
>> lua_resume(N1, NULL, 0);
>> if(N1 != L1 && resume_main) lua_resume(L1, NULL, 0);
>> N1 = resume_thread;
>>
>> resume_main = 1;
>> resume_thread = L2;
>> lua_resume(N2, NULL, 0);
>> if(N2 != L2 && resume_main) lua_resume(L2, NULL, 0);
>> N2 = resume_thread;
>>
>> }
>> }
>>
>> /*
>>
>> % ./a.out | uniq -c | head
>> 100 B
>> 70 A
>> 21 B
>> 125 C
>> 79 B
>> 70 A
>> 44 B
>> 125 C
>> 56 B
>> 70 A
>>
>> */
>>
>> nicolas.
>>
>> On 3/31/14, Milind Gupta <milind.gupta@gmail.com> wrote:
>> > Here is a crude round robin schedules I had tried but had not tried
>> > coroutines in the lua code. This scheme is working good for me:
>> >
>> > #include <stdio.h>
>> > #include <string.h>
>> > #include "lua.h"
>> > #include "lualib.h"
>> > #include "lauxlib.h"
>> >
>> >
>> > int flag = 0;
>> > lua_State *luaVM1, *luaVM2, *thread1, *thread2;
>> > int hookFunc(lua_State *L, lua_Debug *dbg);
>> >
>> > int main(int argc, char* argv[ ])
>> > {
>> > luaVM1 = luaL_newstate();
>> > luaVM2 = luaL_newstate();
>> >
>> > luaL_openlibs(luaVM1);
>> > luaL_openlibs(luaVM2);
>> >
>> > thread1 = lua_newthread(luaVM1);
>> > thread2 = lua_newthread(luaVM2);
>> >
>> > if (NULL == luaVM1 || NULL == luaVM2)
>> > {
>> > printf("Error Initializing lua\n");
>> > return -1;
>> > }
>> > char* prog1 = "for i = 1,5 do print('x'..tostring(i)) a=io.read()
>> > print(a) end";
>> > char* prog2 = "for i = 1,10 do print('y'..tostring(i)) end";
>> > // Create threads in each lua state
>> > // Now push the function into the stack of each thread
>> > luaL_loadstring(thread1,prog1);
>> > luaL_loadstring(thread2,prog2);
>> > lua_sethook(thread1,(lua_Hook) hookFunc,LUA_MASKCOUNT,4);
>> > lua_sethook(thread2,(lua_Hook) hookFunc,LUA_MASKCOUNT,4);
>> >
>> > lua_resume(thread1,0);
>> > flag=1;
>> > lua_resume(thread2,0);
>> > while(lua_status(thread1) || lua_status(thread2))
>> > {
>> > if (flag==0)
>> > {
>> > flag = 1;
>> > if (lua_status(thread2))
>> > lua_resume(thread2,0);
>> > }
>> > else
>> > {
>> > flag = 0;
>> > if (lua_status(thread1))
>> > lua_resume(thread1,0);
>> > }
>> > }
>> >
>> >
>> > lua_close( luaVM1 );
>> > lua_close( luaVM2 );
>> >
>> > return 0;
>> > }
>> >
>> > int hookFunc(lua_State *L, lua_Debug *dbg)
>> > {
>> > printf("Hook Called\n");
>> > if(flag==0)
>> > {
>> > printf("Flag0\n");
>> > return lua_yield(thread1,0);
>> > }
>> > else
>> > {
>> > printf("flag1\n");
>> > return lua_yield(thread2,0);
>> > }
>> > return 0;
>> > }
>> >
>> >
>> >
>> > On Mon, Mar 31, 2014 at 7:53 AM, Milind Gupta
>> > <milind.gupta@gmail.com>wrote:
>> >
>> >> I have my debug hook function as int and don't have issues although I
>> >> don't use coroutines. Here is an excerpt from Programming in Lua 2nd
>> >> Edition in the Threads chapter:
>> >>
>> >> "
>> >> Standard Lua cannot yield across C function calls. This restriction
>> >> implies
>> >> that a C function cannot suspend itself. The only way for a C function
>> to
>> >> yield is
>> >> when returning, so that it actually does not suspend itself, but its
>> >> caller--which
>> >> should be a Lua function. To suspend its caller, a C function must
>> >> call
>> >> lua_yield
>> >> in the following way:
>> >> return lua_yield(L, nres);
>> >> "
>> >>
>> >>
>> >> On Mon, Mar 31, 2014 at 7:46 AM, Dominique Torette <
>> >> Dominique.Torette@spacebel.be> wrote:
>> >>
>> >>> From 'lua.h', debug hooks are void functions:
>> >>>
>> >>>
>> >>>
>> >>> typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);
>> >>>
>> >>>
>> >>>
>> >>> Regards, Dominique.
>> >>>
>> >>>
>> >>>
>> >>> *From:* lua-l-bounces@lists.lua.org [mailto:
>> lua-l-bounces@lists.lua.org]
>> >>> *On
>> >>> Behalf Of *Milind Gupta
>> >>> *Sent:* lundi 31 mars 2014 16:34
>> >>> *To:* Lua mailing list
>> >>> *Subject:* Re: Pre-emptive round robin scheduler around Lua VM
>> >>>
>> >>>
>> >>>
>> >>> Hi,
>> >>>
>> >>> One thing I have seen in the Programming in Lua book is
>> >>> that
>> >>> the Hook function in C should always have a yield in the return
>> >>> statement
>> >>> so the debug_hook function should not be void and the last statement
>> >>> should
>> >>> be return lua_yield. Does that get rid of the interactions?
>> >>>
>> >>> Regards,
>> >>> Milind
>> >>>
>> >>>
>> >>>
>> >>> On Mon, Mar 31, 2014 at 7:03 AM, Dominique Torette <
>> >>> Dominique.Torette@spacebel.be> wrote:
>> >>>
>> >>> Hi,
>> >>>
>> >>>
>> >>>
>> >>> I'm trying to build a kind of pre-emptive scheduler around Lua VM
>> >>> 5.2.
>> >>>
>> >>> The idea is to execute different lua_State in "parallel'.
>> >>>
>> >>> To give the illusion of parallelism, the idea is to run a thread for
>> >>> a
>> >>> given number of Lua VM instructions and then run the next thread in a
>> >>> list
>> >>> for this number of instructions and so on...
>> >>>
>> >>> From the LUA regular API, when starting the execution of a thread, it
>> is
>> >>> not possible to control the number of Lua VM instructions to execute.
>> >>>
>> >>> But from the LUA debug API, it is possible to define a 'hook' to
>> execute
>> >>> every COUNT of instructions.
>> >>>
>> >>> The first idea was to install such hook and perform the round-robin
>> >>> scheduling from the hook. The lua_State of active thread seems to be
>> >>> saved
>> >>> before running such hook.
>> >>>
>> >>> But I didn't found any means to overwrite the thread to be resumed
>> >>> from
>> >>> the hook.
>> >>>
>> >>> Then the idea was to 'yield' from the hook, back to the round robin
>> >>> scheduler.
>> >>>
>> >>> This seems to work in the simplest cases. But I've noticed some
>> >>> strange
>> >>> "intereferences" when thread use coroutines on its own.
>> >>>
>> >>>
>> >>>
>> >>> The Lua resume API has a 'from' parameter: int lua_resume (lua_State
>> *L,
>> >>> lua_State *from, int nargs);
>> >>>
>> >>> But from the description, I didn't catch the how this param has to be
>> >>> used.
>> >>>
>> >>>
>> >>>
>> >>> I've written a small "C" main program to illustrate the concept and
>> >>> the
>> >>> "interferences"...
>> >>>
>> >>> In the program here below, the first iteration of the loop works as
>> >>> expected.
>> >>>
>> >>> Then the L[0] and its coroutine are resumed, but the hook is reached
>> >>> faster than for the first iteration and the L[1] is rescheduled.
>> >>>
>> >>> After L[0] will be never rescheduled, only L[1].
>> >>>
>> >>>
>> >>>
>> >>> Thanks in advance, Dominique Torette.
>> >>>
>> >>>
>> >>>
>> >>> #include "lua.h"
>> >>>
>> >>> #include "lauxlib.h"
>> >>>
>> >>> #include "lualib.h"
>> >>>
>> >>> #include "lstate.h"
>> >>>
>> >>> #include <stdio.h>
>> >>>
>> >>> #include <setjmp.h>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> lua_State* L[2];
>> >>>
>> >>> lua_State* S[2];
>> >>>
>> >>> int current;
>> >>>
>> >>> int previous;
>> >>>
>> >>>
>> >>>
>> >>> void debug_hook (lua_State *X, lua_Debug *ar)
>> >>>
>> >>> {
>> >>>
>> >>>
>> >>>
>> >>> printf("In debug_hook\n");
>> >>>
>> >>> if((X->l_G)->mainthread != X)
>> >>>
>> >>> {
>> >>>
>> >>> printf("from coroutine \n");
>> >>>
>> >>> }
>> >>>
>> >>> S[current] = X;
>> >>>
>> >>> current = (current+1)%2;
>> >>>
>> >>> lua_yield ((X->l_G)->mainthread,0);
>> >>>
>> >>> }
>> >>>
>> >>>
>> >>>
>> >>> int main(int argc, char * argv)
>> >>>
>> >>> {
>> >>>
>> >>> int status;
>> >>>
>> >>>
>> >>>
>> >>> L[0] = luaL_newstate();
>> >>>
>> >>> luaL_openlibs(L[0]);
>> >>>
>> >>>
>> >>>
>> >>> luaL_loadstring(L[0], "co = coroutine.create(function ()
>> >>> while
>> >>> true do print('hi') coroutine.yield() end end) while true do
>> >>> print('hello')
>> >>> coroutine.resume(co) end");
>> >>>
>> >>> lua_sethook (L[0],debug_hook,LUA_MASKCOUNT,500);
>> >>>
>> >>>
>> >>>
>> >>> L[1] = luaL_newstate();
>> >>>
>> >>> luaL_openlibs(L[1]);
>> >>>
>> >>> luaL_loadstring(L[1], "while true do print('world') end");
>> >>>
>> >>> lua_sethook (L[1],debug_hook,LUA_MASKCOUNT,500);
>> >>>
>> >>>
>> >>>
>> >>> current = 0;
>> >>>
>> >>> S[0] = L[0];
>> >>>
>> >>> S[1] = L[1];
>> >>>
>> >>> for(;;)
>> >>>
>> >>> {
>> >>>
>> >>> printf("Resume 1\n");
>> >>>
>> >>> status = lua_resume (S[0],L[0],0);
>> >>>
>> >>> printf("status 1 %d\n",status);
>> >>>
>> >>> printf("Resume 2\n");
>> >>>
>> >>> status = lua_resume (S[1],L[1],0);
>> >>>
>> >>> printf("status 2 %d\n",status);
>> >>>
>> >>> printf("Reloop\n");
>> >>>
>> >>> }
>> >>>
>> >>> }
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> [image:
>> >>> http://www.spacebel.be/wp-content/uploads/2011/06/image-sign-sbp.jpg]
>> >>>
>> >>> *Dominique Torette*
>> >>> System Architect
>> >>> Rue des Chasseurs Ardennais - Liège Science Park - B-4031 Angleur
>> >>> Tel: +32 (0) 4 361 81 11 - Fax: +32 (0) 4 361 81 20
>> >>> www.spacebel.be
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
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>
