nmeter: 4k buffers are too small for /proc files,

 make them dynamically sized with 16k upper limit. +75 bytes

diff --git a/procps/nmeter.c b/procps/nmeter.c
index cded67e562868643a4757d43ea29cbfeb9f43e07..068c739fb8efeb062c0c2131d42341ba6ffab1af 100644 (file)
--- a/procps/nmeter.c
+++ b/procps/nmeter.c
@@ -22,11 +22,14 @@
 
 typedef unsigned long long ullong;
 
-enum { PROC_FILE_SIZE = 4096 };
+enum {  /* Preferably use powers of 2 */
+       PROC_MIN_FILE_SIZE = 256,
+       PROC_MAX_FILE_SIZE = 16 * 1024,
+};
 
 typedef struct proc_file {
        char *file;
-       //const char *name;
+       int file_sz;
        smallint last_gen;
 } proc_file;
 
@@ -124,30 +127,42 @@ static void put_question_marks(int count)
                put_c('?');
 }
 
-static void readfile_z(char *buf, int sz, const char* fname)
+static void readfile_z(proc_file *pf, const char* fname)
 {
 // 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);
+       int fd;
+       int sz, rdsz;
+       char *buf;
+
+       sz = pf->file_sz;
+       buf = pf->file;
+       if (!buf) {
+               buf = xmalloc(PROC_MIN_FILE_SIZE);
+               sz = PROC_MIN_FILE_SIZE;
+       }
+ again:
+       fd = xopen(fname, O_RDONLY);
        buf[0] = '\0';
-       sz = read(fd, buf, sz - 1);
-       if (sz > 0)
-               buf[sz] = '\0';
+       rdsz = read(fd, buf, sz-1);
        close(fd);
+       if (rdsz > 0) {
+               if (rdsz == sz-1 && sz < PROC_MAX_FILE_SIZE) {
+                       sz *= 2;
+                       buf = xrealloc(buf, sz);
+                       goto again;
+               }
+               buf[rdsz] = '\0';
+       }
+       pf->file_sz = sz;
+       pf->file = buf;
 }
 
 static const char* get_file(proc_file *pf)
 {
        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, proc_name[pf - &first_proc_file]);
+               readfile_z(pf, proc_name[pf - &first_proc_file]);
        }
        return pf->file;
 }