nmeter: stop using data/bss; reduce amount of reads from /proc

# size */*/nmeter.o
   text    data     bss     dec     hex filename
   4366      80      16    4462    116e busybox.t0/miscutils/nmeter.o
   4386       0       0    4386    1122 busybox.t2/miscutils/nmeter.o

diff --git a/miscutils/nmeter.c b/miscutils/nmeter.c
index e15cc8c71eb81bc55c461563480342f65ce1d168..3152b74e31f6a08544b63a6f1a4b233163342d3f 100644 (file)
--- a/miscutils/nmeter.c
+++ b/miscutils/nmeter.c
@@ -17,33 +17,67 @@
 
 typedef unsigned long long ullong;
 
-enum { proc_file_size = 4096 };
+enum { PROC_FILE_SIZE = 4096 };
 
 typedef struct proc_file {
-       const char *name;
-       int gen;
        char *file;
+       //const char *name;
+       smallint last_gen;
 } proc_file;
 
-static proc_file proc_stat = { "/proc/stat", -1 };
-static proc_file proc_loadavg = { "/proc/loadavg", -1 };
-static proc_file proc_net_dev = { "/proc/net/dev", -1 };
-static proc_file proc_meminfo = { "/proc/meminfo", -1 };
-static proc_file proc_diskstats = { "/proc/diskstats", -1 };
-// Sample #
-static int gen = -1;
-// Linux 2.6? (otherwise assumes 2.4)
-static int is26 = 0;
-static struct timeval tv;
-static int delta = 1000000;
-static int deltanz = 1000000;
-static int need_seconds = 0;
-static const char *final_str = "\n";
+static const char *const proc_name[] = {
+       "stat",         // Must match the order of proc_file's!
+       "loadavg",
+       "net/dev",
+       "meminfo",
+       "diskstats",
+       "sys/fs/file-nr",
+};
+
+struct globals {
+       // Sample generation flip-flop
+       smallint gen;
+       // Linux 2.6? (otherwise assumes 2.4)
+       smallint is26;
+       // 1 if sample delay is not an integer fraction of a second
+       smallint need_seconds;
+       char *cur_outbuf;
+       const char *final_str;
+       int delta;
+       int deltanz;
+       struct timeval tv;
+#define first_proc_file proc_stat
+       proc_file proc_stat;    // Must match the order of proc_name's!
+       proc_file proc_loadavg;
+       proc_file proc_net_dev;
+       proc_file proc_meminfo;
+       proc_file proc_diskstats;
+       proc_file proc_sys_fs_filenr;
+};
+#define G (*ptr_to_globals)
+#define gen                (G.gen               )
+#define is26               (G.is26              )
+#define need_seconds       (G.need_seconds      )
+#define cur_outbuf         (G.cur_outbuf        )
+#define final_str          (G.final_str         )
+#define delta              (G.delta             )
+#define deltanz            (G.deltanz           )
+#define tv                 (G.tv                )
+#define proc_stat          (G.proc_stat         )
+#define proc_loadavg       (G.proc_loadavg      )
+#define proc_net_dev       (G.proc_net_dev      )
+#define proc_meminfo       (G.proc_meminfo      )
+#define proc_diskstats     (G.proc_diskstats    )
+#define proc_sys_fs_filenr (G.proc_sys_fs_filenr)
 
 // We depend on this being a char[], not char* - we take sizeof() of it
 #define outbuf bb_common_bufsiz1
-static char *cur_outbuf = outbuf;
 
+#define INIT_G() do { \
+               cur_outbuf = outbuf; \
+               final_str = "\n"; \
+               deltanz = delta = 1000000; \
+       } while (0)
 
 static inline void reset_outbuf(void)
 {
@@ -85,27 +119,31 @@ static void put_question_marks(int count)
                put_c('?');
 }
 
-static int readfile_z(char *buf, int sz, const char* fname)
+static void readfile_z(char *buf, int sz, const char* fname)
 {
-       sz = open_read_close(fname, buf, sz-1);
-       if (sz < 0) {
-               buf[0] = '\0';
-               return 1;
+// open_read_close() will do two reads in order to be sure we are at EOF,
+// and we don't need/want that.
+//     sz = open_read_close(fname, buf, sz-1);
+
+       int fd = xopen(fname, O_RDONLY);
+       buf[0] = '\0';
+       if (fd >= 0) {
+               sz = read(fd, buf, sz-1);
+               if (sz > 0) buf[sz] = '\0';
+               close(fd);
        }
-       buf[sz] = '\0';
-       return 0;
 }
 
 static const char* get_file(proc_file *pf)
 {
-       if (pf->gen != gen) {
-               pf->gen = gen;
-               // We allocate proc_file_size bytes. This wastes memory,
+       if (pf->last_gen != gen) {
+               pf->last_gen = gen;
+               // We allocate PROC_FILE_SIZE bytes. This wastes memory,
                // but allows us to allocate only once (at first sample)
                // per proc file, and reuse buffer for each sample
                if (!pf->file)
-                       pf->file = xmalloc(proc_file_size);
-               readfile_z(pf->file, proc_file_size, pf->name);
+                       pf->file = xmalloc(PROC_FILE_SIZE);
+               readfile_z(pf->file, PROC_FILE_SIZE, proc_name[pf - &first_proc_file]);
        }
        return pf->file;
 }
@@ -242,10 +280,10 @@ static s_stat* init_literal(void)
 
 static s_stat* init_delay(const char *param)
 {
-       delta = strtol(param, NULL, 0)*1000;
+       delta = bb_strtoi(param, NULL, 0) * 1000;
        deltanz = delta > 0 ? delta : 1;
        need_seconds = (1000000%deltanz) != 0;
-       return (s_stat*)0;
+       return NULL;
 }
 
 static s_stat* init_cr(const char *param)
@@ -281,7 +319,7 @@ static void collect_cpu(cpu_stat *s)
                return;
        }
 
-       for (i=0; i<CPU_FIELDCNT; i++) {
+       for (i = 0; i < CPU_FIELDCNT; i++) {
                ullong old = s->old[i];
                if (data[i] < old) old = data[i];               //sanitize
                s->old[i] = data[i];
@@ -289,7 +327,7 @@ static void collect_cpu(cpu_stat *s)
        }
 
        if (all) {
-               for (i=0; i<CPU_FIELDCNT; i++) {
+               for (i = 0; i < CPU_FIELDCNT; i++) {
                        ullong t = bar_sz * data[i];
                        norm_all += data[i] = t / all;
                        frac[i] = t % all;
@@ -298,7 +336,7 @@ static void collect_cpu(cpu_stat *s)
                while (norm_all < bar_sz) {
                        unsigned max = frac[0];
                        int pos = 0;
-                       for (i=1; i<CPU_FIELDCNT; i++) {
+                       for (i = 1; i < CPU_FIELDCNT; i++) {
                                if (frac[i] > max) max = frac[i], pos = i;
                        }
                        frac[pos] = 0;  //avoid bumping up same value twice
@@ -640,11 +678,9 @@ S_STAT_END(fd_stat)
 
 static void collect_fd(fd_stat *s)
 {
-       char file[4096];
        ullong data[2];
 
-       readfile_z(file, sizeof(file), "/proc/sys/fs/file-nr");
-       if (rdval(file, "", data, 1, 2)) {
+       if (rdval(get_file(&proc_sys_fs_filenr), "", data, 1, 2)) {
                put_question_marks(4);
                return;
        }
@@ -702,7 +738,7 @@ static s_stat* init_time(const char *param)
 
 static void collect_info(s_stat *s)
 {
-       gen++;
+       gen ^= 1;
        while (s) {
                put(s->label);
                s->collect(s);
@@ -714,7 +750,7 @@ static void collect_info(s_stat *s)
 typedef s_stat* init_func(const char *param);
 
 static const char options[] = "ncmsfixptbdr";
-static init_func* init_functions[] = {
+static init_func *const init_functions[] = {
        init_if,
        init_cpu,
        init_mem,
@@ -738,10 +774,15 @@ int nmeter_main(int argc, char **argv)
        s_stat *s;
        char *cur, *prev;
 
+       PTR_TO_GLOBALS = xzalloc(sizeof(G));
+       INIT_G();
+
+       xchdir("/proc");
+
        if (argc != 2)
                bb_show_usage();
 
-       if (open_read_close("/proc/version", buf, sizeof(buf)) > 0)
+       if (open_read_close("version", buf, sizeof(buf)) > 0)
                is26 = (strstr(buf, " 2.4.")==NULL);
 
        // Can use argv[1] directly, but this will mess up
@@ -750,11 +791,11 @@ int nmeter_main(int argc, char **argv)
        while (1) {
                char *param, *p;
                prev = cur;
-again:
+ again:
                cur = strchr(cur, '%');
                if (!cur)
                        break;
-               if (cur[1]=='%') {      // %%
+               if (cur[1] == '%') {    // %%
                        strcpy(cur, cur+1);
                        cur++;
                        goto again;
@@ -813,12 +854,12 @@ again:
        collect_info(first);
        reset_outbuf();
        if (delta >= 0) {
-               gettimeofday(&tv, 0);
+               gettimeofday(&tv, NULL);
                usleep(delta > 1000000 ? 1000000 : delta - tv.tv_usec%deltanz);
        }
 
        while (1) {
-               gettimeofday(&tv, 0);
+               gettimeofday(&tv, NULL);
                collect_info(first);
                put(final_str);
                print_outbuf();
@@ -831,9 +872,9 @@ again:
                if (delta >= 0) {
                        int rem;
                        // can be commented out, will sacrifice sleep time precision a bit
-                       gettimeofday(&tv, 0);
+                       gettimeofday(&tv, NULL);
                        if (need_seconds)
-                               rem = delta - ((ullong)tv.tv_sec*1000000+tv.tv_usec)%deltanz;
+                               rem = delta - ((ullong)tv.tv_sec*1000000 + tv.tv_usec) % deltanz;
                        else
                                rem = delta - tv.tv_usec%deltanz;
                        // Sometimes kernel wakes us up just a tiny bit earlier than asked
@@ -845,5 +886,5 @@ again:
                }
        }
 
-       return 0;
+       /*return 0;*/
 }