$ grep -R . /proc/pressure/
/proc/pressure/io:some avg10=0.00 avg60=0.00 avg300=0.00 total=10587199096
/proc/pressure/io:full avg10=0.00 avg60=0.00 avg300=0.00 total=10072568253
/proc/pressure/cpu:some avg10=30.27 avg60=29.97 avg300=18.80 total=1620253162
/proc/pressure/memory:some avg10=0.00 avg60=0.00 avg300=0.00 total=15411
/proc/pressure/memory:full avg10=0.00 avg60=0.00 avg300=0.00 total=12389
$ uptime
07:24:59 up 2 days, 16:15,  1 user,  load average: 150.58, 118.00, 76.42

$ grep -R . /proc/pressure/
/proc/pressure/io:some avg10=15.60 avg60=11.13 avg300=7.98 total=94192093351
/proc/pressure/io:full avg10=15.60 avg60=11.13 avg300=7.97 total=93713900789
/proc/pressure/cpu:some avg10=0.00 avg60=0.00 avg300=0.00 total=1159442298
/proc/pressure/memory:some avg10=67.79 avg60=67.80 avg300=72.51 total=618948360599
/proc/pressure/memory:full avg10=67.60 avg60=67.58 avg300=72.18 total=613900281165

some|full Stall_Amount Time_Window

01 #include <errno.h>
02 #include <fcntl.h>
03 #include <stdio.h>
04 #include <poll.h>
05 #include <string.h>
06 #include <unistd.h>
07 /*
08  * Monitor memory partial stall with 1s tracking
09  * window size and 150ms threshold.
10  */
11 int main() {
12   const char trig[] = "some 150000 1000000";
13   struct pollfd fds;
14   int n;
15   fds.fd = open("/proc/pressure/memory",
16                  O_RDWR | O_NONBLOCK);
17   if (fds.fd < 0) {
18     printf("/proc/pressure/memory open error: %s\n",
19             strerror(errno));
20     return 1;
21   }
22   fds.events = POLLPRI;
23   if (write(fds.fd, trig, strlen(trig) + 1) < 0) {
24     printf("/proc/pressure/memory write error: %s\n",
25             strerror(errno));
26     return 1;
27   }
28   printf("waiting for events...\n");
29   while (1) {
30     n = poll(&fds, 1, -1);
31     if (n < 0) {
32       printf("poll error: %s\n", strerror(errno));
33       return 1;
34     }
35     if (fds.revents & POLLERR) {
36       printf("got POLLERR, event source is gone\n");
37       return 0;
38     }
39     if (fds.revents & POLLPRI) {
40       printf("event triggered!\n");
41     } else {
42       printf("unknown event received: 0x%x\n",
43               fds.revents);
44       return 1;
45     }
46   }
47   return 0;
48 }