bfc93a3ca
Denis Vlasenko
2008-09-26
Subject
nmeter: 4k buffers are too small for /proc files, make them dynamically sized with 16k upper limit. +75 bytes
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procps/nmeter.c+30 -15
| @@ -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; | |
| } | |