555be9b857
Make meminfo-writer compute used memory, and report to qmemman only if it has changed significantly enough. As it is written in C, its code is much faster that qmemman-server; also in the idle case, it saves on xenstore communication overhead. Allows to send updates up to 10 times per second, with CPU load on the VM below 0.1%.
121 lines
2.5 KiB
C
121 lines
2.5 KiB
C
#include <fcntl.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <xs.h>
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#include <syslog.h>
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#include <string.h>
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unsigned long prev_used_mem;
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int used_mem_change_threshold;
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int delay;
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char *parse(char *buf)
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{
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char *ptr = buf;
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char name[256];
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static char outbuf[4096];
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int val;
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int len;
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int MemTotal=0, MemFree=0, Buffers=0, Cached=0, SwapTotal=0, SwapFree=0;
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unsigned long long key;
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long used_mem, used_mem_diff;
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int nitems = 0;
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while (nitems != 6) {
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sscanf(ptr, "%s %d kB\n%n", name, &val, &len);
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key = *(unsigned long long *) ptr;
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if (key == *(unsigned long long *) "MemTotal:") {
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MemTotal = val;
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nitems++;
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} else if (key == *(unsigned long long *) "MemFree:") {
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MemFree = val;
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nitems++;
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} else if (key == *(unsigned long long *) "Buffers:") {
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Buffers = val;
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nitems++;
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} else if (key == *(unsigned long long *) "Cached: ") {
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Cached = val;
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nitems++;
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} else if (key == *(unsigned long long *) "SwapTotal:") {
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SwapTotal = val;
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nitems++;
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} else if (key == *(unsigned long long *) "SwapFree:") {
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SwapFree = val;
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nitems++;
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}
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ptr += len;
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}
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used_mem =
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MemTotal - Buffers - Cached - MemFree + SwapTotal - SwapFree;
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if (used_mem < 0)
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return NULL;
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used_mem_diff = used_mem - prev_used_mem;
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prev_used_mem = used_mem;
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if (used_mem_diff < 0)
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used_mem_diff = -used_mem_diff;
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if (used_mem_diff > used_mem_change_threshold) {
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sprintf(outbuf,
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"MemTotal: %d kB\nMemFree: %d kB\nBuffers: %d kB\nCached: %d kB\n"
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"SwapTotal: %d kB\nSwapFree: %d kB\n", MemTotal,
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MemFree, Buffers, Cached, SwapTotal, SwapFree);
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return outbuf;
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}
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return NULL;
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}
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void usage()
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{
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fprintf(stderr,
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"usage: meminfo_writer threshold_in_kb delay_in_us\n");
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exit(1);
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}
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void send_to_qmemman(struct xs_handle *xs, char *data)
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{
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if (!xs_write(xs, XBT_NULL, "memory/meminfo", data, strlen(data))) {
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syslog(LOG_DAEMON | LOG_ERR, "error writing xenstore ?");
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exit(1);
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}
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}
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int
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main(int argc, char **argv)
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{
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char buf[4096];
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int n;
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char *meminfo_data;
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int fd;
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struct xs_handle *xs;
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if (argc != 3)
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usage();
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used_mem_change_threshold = atoi(argv[1]);
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delay = atoi(argv[2]);
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if (!used_mem_change_threshold || !delay)
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usage();
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fd = open("/proc/meminfo", O_RDONLY);
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if (fd < 0) {
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perror("open meminfo");
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exit(1);
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}
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xs = xs_domain_open();
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if (!xs) {
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perror("xs_domain_open");
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exit(1);
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}
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for (;;) {
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n = read(fd, buf, sizeof(buf));
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buf[n] = 0;
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meminfo_data = parse(buf);
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if (meminfo_data)
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send_to_qmemman(xs, meminfo_data);
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usleep(delay);
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lseek(fd, 0, SEEK_SET);
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}
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}
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