blacknon / hwatch

Hi,
hwatch is a great tool. However, I noticed that its CPU consumption is very high.
A simple hwatch -n 10 date consumes about 20% CPU on an i7-5557U CPU (tested with version 0.3.3 on Ubuntu 22.04 with kernel 5.15.0-27-generic).
Here's a strace output when I let it run for about 20 seconds:

strace -C hwatch -n 10 date
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 99.98    1.295830      323957         4           futex
  0.01    0.000128          42         3           munmap
  0.00    0.000036           6         6           open
  0.00    0.000024          24         1           madvise
  0.00    0.000015           1         9           write
  0.00    0.000014           2         6           fcntl
  0.00    0.000013           2         6           close
  0.00    0.000009           0        11           ioctl
  0.00    0.000000           0         1           poll
  0.00    0.000000           0         6           mmap
  0.00    0.000000           0         3           mprotect
  0.00    0.000000           0       125           brk
  0.00    0.000000           0         5           rt_sigaction
  0.00    0.000000           0         8           rt_sigprocmask
  0.00    0.000000           0         2           clone
  0.00    0.000000           0         1           execve
  0.00    0.000000           0         3           sigaltstack
  0.00    0.000000           0         1           arch_prctl
  0.00    0.000000           0         1           set_tid_address
  0.00    0.000000           0         1           getrandom
------ ----------- ----------- --------- --------- ----------------
100.00    1.296069        6384       203           total

Thank you for information!
I have confirmed this issue on Linux (debian 10).

I usually developed it on a Mac, but CPU usage didn't seem to be a problem here. Therefore, it seems that this event could not be confirmed.

From the situation, it is possible that the cause is Mutex lock, used in CommandResult.
Considering how to deal with it.

There is a high possibility of recv_timeout of Receiver.

hwatch/src/app.rs

Line 182 in 3181b94

match self.rx.recv_timeout(Duration::from_secs(60)) {

futex(0x55555658b068, FUTEX_WAIT_PRIVATE, 4294967295, {tv_sec=59, tv_nsec=999998534}) = 0
open("/dev/tty", O_RDONLY|O_CLOEXEC)    = 9
fcntl(9, F_SETFD, FD_CLOEXEC)           = 0
ioctl(9, TIOCGWINSZ, {ws_row=39, ws_col=143, ws_xpixel=1144, ws_ypixel=312}) = 0
close(9)                                = 0
write(1, "\33[1;138H\33[38;5;6m4\33[1;143H5\33[3;3"..., 268) = 268
futex(0x55555658b068, FUTEX_WAIT_PRIVATE, 4294967295, {tv_sec=59, tv_nsec=999998024}) = 0
open("/dev/tty", O_RDONLY|O_CLOEXEC)    = 9
fcntl(9, F_SETFD, FD_CLOEXEC)           = 0
ioctl(9, TIOCGWINSZ, {ws_row=39, ws_col=143, ws_xpixel=1144, ws_ypixel=312}) = 0
close(9)                                = 0
write(1, "\33[1;135H\33[38;5;6m20\33[1;138H0\33[1;"..., 318) = 318
futex(0x55555658b068, FUTEX_WAIT_PRIVATE, 4294967295, {tv_sec=59, tv_nsec=999998211}

Thanks, I can confirm that CPU usage with 0.3.4 is now negligible

Very high CPU consumption