Question

In the redis source I have found “Rss Information”, but I don’t know what this.

If I use Google search with the query string “file rss information”, the only results I get are like “RSS xml feed”.

This is defined in the source:

size_t zmalloc_get_rss(void) {
   int page = sysconf(_SC_PAGESIZE);
   size_t rss;
   char buf[4096];
   char filename[256];
   int fd, count;
   char *p, *x;

   snprintf(filename,256,"/proc/%d/stat",getpid());
   if ((fd = open(filename,O_RDONLY)) == -1) return 0;
   if (read(fd,buf,4096) <= 0) {
       close(fd);
       return 0;
   }
   close(fd);

   p = buf;
   count = 23; /* RSS is the 24th field in /proc/<pid>/stat */
   while(p && count--) {
       p = strchr(p,' ');
       if (p) p++;
   }
   if (!p) return 0;
   x = strchr(p,' ');
   if (!x) return 0;
   *x = '\0';

   rss = strtoll(p,NULL,10);
   rss *= page;
   return rss;
}

Will this get process memory? I can only guess.

Answer 1

Yes, RSS means “resident set size”.

See proc’s manual page:

Resident Set Size: number of pages the process has in real memory. This is just the pages which count toward text, data, or stack space. This does not include pages which have not been demand-loaded in, or which are swapped out.