pv (a pipeline progress indicator) in main?

[Seth Arnold]

On Fri, Apr 22, 2022 at 09:58:14AM -0700, Bryce Harrington wrote:
> LP page:  https://launchpad.net/ubuntu/+source/pv

> Or other considerations that need made before deciding?

pv is popular in the OpenZFS communities for use with zfs send | zfs recv
-- as is mbuffer, which exists more to provide much larger buffering than
the usual libc stdio buffers. mbuffer doesn't have progress bars, but does
show throughput:

$ dd if=/dev/urandom | mbuffer > /dev/null
in @ 32.5 MiB/s, out @ 32.5 MiB/s,  166 MiB total, buffer   0% full^C
341133+0 records in
341133+0 records out
174660096 bytes (175 MB, 167 MiB) copied, 5.13954 s, 34.0 MB/s
mbuffer: warning: error during output to <stdout>: canceled
summary:  167 MiByte in  5.1sec - average of 32.4 MiB/s

One feature of pv that slightly worries me is that you can change the
parameters of an already-running instance by running it again, with -R:

       -R PID, --remote PID
              If PID is an instance of pv that is already running,
              -R PID will cause that instance to act as though it
              had been given this instance's command line instead.
              For example, if pv -L 123K is running with process ID
              9876, then running pv -R 9876 -L 321K will cause it to
              start using a rate limit of 321KiB instead of 123KiB.
              Note that some options cannot be changed while
              running, such as -c, -l, -f, -D, -E, and -S.

It's probably fine. (Afterall, it's possible to disable the yama sysctl
kernel.yama.ptrace_scope and attach a debugger to the process to modify
whatever you want.) But it's also possible it's not fine.

Thanks
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: not available
URL: <https://lists.ubuntu.com/archives/ubuntu-devel/attachments/20220422/eb24e320/attachment.sig>