linux-kernel - Re: A further though on /proc/PID/timens

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Message-ID: <CANaxB-y0ZB223dQgvxvUHRzkn4f-_B2vTzYxe_mi=o+3SJ4yVw@mail.gmail.com>
Date:   Thu, 9 Apr 2020 12:17:52 -0700
From:   Andrey Vagin <avagin@...nvz.org>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc:     Dmitry Safonov <dima@...sta.com>,
        Linux API <linux-api@...r.kernel.org>,
        Containers <containers@...ts.linux-foundation.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Adrian Reber <adrian@...as.de>
Subject: Re: A further though on /proc/PID/timens_offsets

On Tue, Apr 7, 2020 at 6:24 AM Michael Kerrisk (man-pages)
<mtk.manpages@...il.com> wrote:

>        The  clock-id  identifies the clock whose offsets are being shown.
>        This field is either 1, for CLOCK_MONOTONIC, or 7, for CLOCK_BOOT‐
>        TIME.
>
> What was the reason for exposing numeric clock IDs in the
> timens_offsets file? In API terms, that seems a little ugly.
>
> I think it would have been much nicer if the clocks were defined
> symbolically in this file. I.e., that reading the file would have
> shown something like
>
> monotonic    x    y
> boottime     x    y
>
> And that records similarly with symbolic clock names could have
> been written to the file. Was there a reason not to do this?

No, there was not except that I haven't thought about this. I agree
that symbolic clock names looks nicer for humans, but numeric clock
IDs are a bit more convenient when we  need to set/read offsets from
code. This interface is in the released kernel, so I think we can't
change the format of the content of this file. But we can add support
of symbolic clock names for setting clock offsets. What do you think?

Thanks,
Andrei