[Toybox] [PATCH] Add uclampset(1).

[enh]

On Fri, Dec 10, 2021 at 6:52 AM Rob Landley <rob at landley.net> wrote:

> On 12/9/21 7:31 PM, enh via Toybox wrote:
> > No standard, but part of util-linux.
>
> Don't default y in pending.
>

yeah, sorry. i realized that after i'd gone to bed. at least i'm consistent
... i *always* make that mistake.


> USE_TASKSET(NEWTOY(uclampset)) doesn't match.
>

d'oh. _that's_ a new mistake though!


> Does this require root?
>

as you can tell from the previous mistake, i took taskset as a basis for
this. it seemed plausible to me that if taskset needed STAYROOT (which i
assume is what you're asking about here), this would too? but i've no idea.


> From a UI perspective, do we ever _not_ want -a?
>

i wondered that too, but this is what the util-linux one does. (which is
presumably just because that's what taskset does. so -- like me with
`default y` at least they're _consistent_.)


> Sigh. It's HARD to come up with a good terse description of -R.
>

yeah, as you can see, i gave up: "you're going to want to read a man page
--- here's what you should search for" was all i was going for there.


> $ grep syscall\.h toys/*/*.c
> toys/other/chrt.c:#include <sys/syscall.h>
> toys/other/insmod.c:#include <sys/syscall.h>
> toys/other/ionice.c:#include <sys/syscall.h>
> toys/other/nsenter.c:#include <sys/syscall.h>
> toys/other/pivot_root.c:#include <sys/syscall.h>
> toys/other/readahead.c:#include <sys/syscall.h>
> toys/other/rmmod.c:#include <sys/syscall.h>
> toys/other/taskset.c:#include <sys/syscall.h>
> toys/pending/modprobe.c:#include <sys/syscall.h>
> toys/pending/strace.c:#include <sys/syscall.h>
> toys/pending/uclampset.c:#include <sys/syscall.h>
>
> Is there a reason we haven't got sys/syscall.h in toys.h? Sure, it's not in
> posix but it apparently originated in BSD:
>
> https://www.freebsd.org/cgi/man.cgi?query=syscall&sektion=2&format=html
>
> So the header should at least _exist_ there, and including it not break
> the build?
>

yeah, there's a <sys/syscall.h> on macOS too. (iirc it's the glibc
<syscall.h> synonym that's less portable.)


> Ah. My devauan kernel is 4.19+fixes, so this goes boing when I run it.
> Luckily,
> I created mkroot... Hmmm... Except when I tried your version (without any
> of my
> changes), it still went:
>
> Type exit when done.
> # uclampset
> uclampset: Need -p PID or CMD [ARG...]
> # uclampset -p $$
> sh (48) util_clamp: min: 0 max: 0
> # uclampset -p $$ -m 42
> uclampset: sched_setattr for pid 48: Not supported
> # uclampset -p $$ -M 42
> uclampset: sched_setattr for pid 48: Not supported
> # cat /proc/version
> Linux version 5.16.0-rc3 (landley at driftwood) (x86_64-linux-musl-gcc (GCC)
> 9.2.01
>
> Do I need a kernel config entry or something?
>

i think so, yes. i got similar results to you on my laptop, but running on
an x86-64 [virtual] device everything worked [to the extent that "i got
back the values i put in, and plausible looking numbers from other stuff"].

i'm guessing it's these?

vsoc_x86_64:/# gzip -dc /proc/config.gz | grep UCLAMP
CONFIG_UCLAMP_TASK=y
CONFIG_UCLAMP_BUCKETS_COUNT=20
CONFIG_UCLAMP_TASK_GROUP=y

(i don't have /proc/config.gz on my laptop though, so i can't check.)

Rob
>
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