const data and pmap output and "+Olit" option

[tanmay patil]

Hi ,

I am trying to optimise memory utilisation for my program
There are some read only arrays in applications which have been declared as static . I changed them to const .
when created shared library ; i got difference in size command , but pmap does not show any difference

----> stats.c
#include

const int x[] = {0 ,1 ,2 ,3 ,4 ,5 ,6 ,7 ,8 ,9 ,10 ,11 ,12 ,13 ,14 ,15 ,16 ,17 ,18 ,19 ,20 ,21 ,22 ,23 ,24 ,25 ,26
,27 ,28 ,29 ,30 ,31 ,32 ,33 ,34 ,35 ,36 ,37 ,38 ,39 ,40 ,41 ,42 ,43 ,44 ,45 ,46 ,47 ,48 ,49 ,50 ,51 ,52 ,53 ,54 ,5
5 ,56 ,57 ,58 ,59 ,60 ,61 ,62 ,63 ,64 ,65 ,66 ,67 ,68 ,69 ,70 ,71 ,72 ,73 ,74 ,75 ,76 ,77 ,78 ,79 ,80 ,81 ,82 ,83
,84 ,85 ,86 ,87 ,88 ,89 ,90 ,91 ,92 ,93 ,94 ,95 ,96 ,97 ,98 ,99 ,100 ,101 ,102 ,103 ,104 ,105 ,106 ,107 ,108 ,109
,110 ,111 ,112 ,113 ,114 ,115 ,116 ,117 ,118 ,119 ,120 ,121 ,122 ,123 ,124 ,125 ,126 ,127 ,128 ,129 ,130 ,131 ,132
,133 ,134 ,135 ,136 ,137 ,138 ,139 ,140 ,141 ,142 ,143 ,144 ,145 ,146 ,147 ,148 ,149 ,150 ,151 ,152 ,153 ,154 ,15
5 ,156 ,157 ,158 ,159 ,160 ,161 ,162 ,163 ,164 ,165 ,166 ,167 ,168 ,169 ,170 ,171 ,172 ,173 ,174 ,175 ,176 ,177 ,1
78 ,179 ,180 ,181 ,182 ,183 ,184 ,185 ,186 ,187 ,188 ,189 ,190 ,191 ,192 ,193 ,194 ,195 ,196 ,197 ,198 ,199 ,200 ,
201 ,202 ,203 ,204 ,205 ,206 ,207 ,208 ,209 ,210 ,211 ,212 ,213 ,214 ,215 ,216 ,217 ,218 ,219 ,220 ,221 ,222 ,223
,224 ,225 ,226 ,227 ,228 ,229 ,230 ,231 ,232 ,233 ,234 ,235 ,236 ,237 ,238 ,239 ,240 ,241 ,242 ,243 ,244 ,245 ,246
,247 ,248 ,249 ,250 ,251 ,252 ,253 ,254 ,255 ,256 ,257 ,258 ,259 ,260 ,261 ,262 ,263 ,264 ,265 ,266 ,267 ,268 ,26
9 ,270 ,271 ,272 ,273 ,274 ,275 ,276 ,277 ,278 ,279 ,280 ,281 ,282 ,283 ,284 ,285 ,286 ,287 ,288 ,289 ,290 ,291 ,2
92 ,293 ,294 ,295 ,296 ,297 ,298 ,299 };

static int y = 0;
void dummy()
{
int z;
z=x[0];
printf(" Value of [%d]\n",z);
y++;
printf("Inside dummy %d\n",y);

}
-------------------------------end of stats3.so
int main(int arcg, char* argv[]) {
void * hndl = (void *)0;
void * func = (void *)0;
int ret = 0;
void (*f)();

hndl=dlopen("./stats3.so",RTLD_LAZY|RTLD_GLOBAL);
/*hndl=dlopen("/finacle/fincore/v10.22BT1/runtime/mbdapirel/prodbase/exe/finlistvalrtn_fab.so",RTLD_LAZY|R
TLD_GLOBAL);*/
/*hndl=dlopen(argv[1],RTLD_LAZY|RTLD_GLOBAL);*/
if (hndl == NULL) {
printf("Unable to load library dlerror [%s]\n", dlerror());
exit(-256);
}

f =(void (*)())dlsym(hndl,"dummy");
if ( f == NULL)
{
printf(" f is null\n");
}
else
{
f();
}
} // end of main

size command with const
text data bss dec hex filename
2140 28 24 2192 890 stats3.so
size command with static arrays instead of const
938 1236 24 2198 896 stats1.so


But when i load these SO using loadlib program
I don't see any difference in pmap output .i was expecting that data and text memory map would be exchanged in case of static and const data . Tried with +Olit=all compiler option . But same result i could see.

502: loadlib
OFFSET VSZ RSZ TYPE PRM FILE
0 4K 4K SD(735) r-- [nullderef]
4000000 4K 4K SC(3) r-x [text]
40010000 32K 28K PD rw- [data]
678d6000 4K 4K PD rw- /users3/e51569/finaclelite/olit/stats3.so
678d7000 4K 4K PD rw- [anonymous]
678d8000 16K 16K PD rwx [anonymous]
678dc000 32K 32K PD rw- /usr/lib/hpux32/libc.so.1
678e4000 48K 48K PD rw- [anonymous]
678f0000 16K 16K PD rwx [anonymous]
678f4000 8K 8K PD rwx [anonymous]
678f6000 4K 4K PD rw- /usr/lib/hpux32/libdl.so.1
678f7000 12K 12K PD rw- /usr/lib/hpux32/dld.so
678fa000 8K 8K PD rw- [anonymous]
678fc000 8K 8K PD rwx [anonymous]
678fe000 4K 4K PD rw- /usr/lib/hpux32/uld.so
678ff000 8K 4K PD rw- [rsestack]
68100000 64K 64K PD rw- [stack]
c0004000 64K 60K SC(691) --x /usr/lib/hpux32/uld.so
c0014000 560K 560K SC(692) r-x /usr/lib/hpux32/dld.so
c01a4000 2820K 2776K SC(692) r-x /usr/lib/hpux32/libc.so.1
c0468000 16K 16K SC(692) r-x /usr/lib/hpux32/libdl.so.1
c07ff000 4K 4K SC(3) r-x /users3/e51569/finaclelite/olit/stats3.so
9fffffff7f7df000 72K 64K PD rw- [uarea]

[Dennis Handly]

>I changed them to const.

Better to be both, even if you are using C++: static const

>I got difference in size command

Then you have solved the problem.

>exit(-256);

You are limited to values 0 .. 255.

>pmap does not show any difference
>I was expecting that data and text memory map would be exchanged in case of static and const data.

Where is your before and after? Unless your data size is many pages, you may not notice it.
What do you mean exchanged? What happens is text increases and data decreases.

>Tried with +Olit=all compiler option.

That's now the default.

Here are your stats3.so regions:
678d6000 4K 4K PD rw- stats3.so
678d7000 4K 4K PD rw- [anonymous]
c07ff000 4K 4K SC(3) r-x stats3.so

Each region is 1 page.