fix large PID overflow their column in top command
Bernhard Reutner-Fischer
rep.dot.nop at gmail.com
Wed Feb 21 20:23:03 UTC 2024
Hi Sukyoung!
please don't top-post
On Mon, 19 Feb 2024 10:22:05 +0000
Matthew Chae <Matthew.Chae at axis.com> wrote:
> Hi Bernhard,
>
> I'm sending new patch and the result of bloatcheck.
> For me, this size is reduced to 135 bytes. What do you think?
Well, 135b is better than the initial 360b :)
> Can you take a look at these attachments?
I'd love to.
But it doesn't apply, unfortunately:
$ git am -s 0004-Allocate-PID-PPID-space-dynamically-in-top-command.patch
Applying: Allocate PID/PPID space dynamically in top command
error: patch failed: procps/top.c:637
error: procps/top.c: patch does not apply
Patch failed at 0001 Allocate PID/PPID space dynamically in top command
hint: Use 'git am --show-current-patch=diff' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".
$ git am --abort
$ patch -p1 -i 0004-Allocate-PID-PPID-space-dynamically-in-top-command.patch
patching file procps/top.c
Hunk #1 FAILED at 637.
Hunk #2 FAILED at 696.
Hunk #3 FAILED at 709.
3 out of 3 hunks FAILED -- saving rejects to file procps/top.c.rej
So I'd have to manually fiddle the patch to apply, which i honestly
don't have time for ATM, as much as i love code-golf in general.
Furthermore (and i'm about to update https://busybox.net/developer
accordingly), for legal reasons, we require a Signed-off-by, as
detailed in
https://www.kernel.org/doc/html/latest/process/submitting-patches.html?highlight=sign%20off#sign-your-work-the-developer-s-certificate-of-origin
so please check you legal department (which should be fine for axis)
and mark your contributions accordingly by 'git commit -s ...' iff this
is in line with your legal situation (again, axis legal will most
likely understand what this is about without much further ado, AFAIK).
>
> PS:
> The function of count_digits() is implemented inside of display_process_list().
> To reduce the size, strlen() is not used.
Did you look if manually outlining count_digits() like you did in the
previous version is beneficial?
And, did you check my previous question if it is better to use the
manual buf "painting", perusing in this case pid_len (for the
compile-time constant 6 as it is now) and ppid_len (ditto), and, for
your other patch on top, username_len (for the current compile-time
constant 8)? The loop to determine the max {,p}pid len is not for free
of course, so it's okish if that manifests size-wise.
PS: 135b is better than the initial suggestion of ~300b, but given
architectures tend to end up with very different codegen per arch and
compilers used, i'm always curious which arch and which compiler
(version) was used to obtain the alleged results. Guess you target
chris with gcc-12-ish?
Stating the target arch usually allows us a rough estimate
about overall impact on other arches.
Many thanks in advance and cheers,
Bernhard
>
> Br-Matthew
>
> ________________________________
> From: Bernhard Reutner-Fischer <rep.dot.nop at gmail.com>
> Sent: Thursday, February 15, 2024 9:46 PM
> To: Matthew Chae <Matthew.Chae at axis.com>
> Cc: rep.dot.nop at gmail.com <rep.dot.nop at gmail.com>; David Laight <David.Laight at ACULAB.COM>; 'Denys Vlasenko' <vda.linux at googlemail.com>; busybox at busybox.net <busybox at busybox.net>; Christopher Wong <Christopher.Wong at axis.com>
> Subject: Re: fix large PID overflow their column in top command
>
> On Wed, 14 Feb 2024 14:05:15 +0000
> Matthew Chae <Matthew.Chae at axis.com> wrote:
>
> > Hi Bernhard,
> >
> > I'm sending new patch and the result of bloatcheck.
>
> Many thanks for the updated patch!
>
> function old new delta
> display_process_list 1406 1765 +359
> .rodata 99721 99724 +3
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 2/0 up/down: 362/0) Total: 362 bytes
> text data bss dec hex filename
> 1009548 16507 1840 1027895 faf37 busybox_old
> 1009910 16507 1840 1028257 fb0a1 busybox_unstripped
>
> I think that's too much. For me this gives +293 bytes, still way too much.
> Can you please see if it helps to retain the manual formatting of
> PID PPID USER?
>
> PS:
>
> procps/top.c: In function ‘display_process_list’:
> procps/top.c:664:1: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
> 664 | typedef struct { unsigned quot, rem; } bb_div_t;
> | ^~~~~~~
>
> so please move your new #define PID_STR block down to right before
> /* what info of the processes is shown */
>
> In
> + int lines = (lines_rem - 1);
> please drop the superfluous braces.
>
> It is most likely not smaller to use
> pid_len = strlen(make_human_readable_str(pid_max,0,0))
> than to introduce this private count_digits(), i fear?
> Maybe we could amortize the addition of count_digits by
> reusing it elsewhere, as a follow-up.
>
> thanks
>
> > Can you review these and give me your thoughts?
> > Just let me know if you think that the code size needs to be reduced.
> >
> > Br-Matthew
> > ________________________________
> > From: Bernhard Reutner-Fischer <rep.dot.nop at gmail.com>
> > Sent: Tuesday, February 13, 2024 7:16 PM
> > To: Matthew Chae <Matthew.Chae at axis.com>
> > Cc: rep.dot.nop at gmail.com <rep.dot.nop at gmail.com>; David Laight <David.Laight at ACULAB.COM>; 'Denys Vlasenko' <vda.linux at googlemail.com>; busybox at busybox.net <busybox at busybox.net>; Christopher Wong <Christopher.Wong at axis.com>
> > Subject: Re: fix large PID overflow their column in top command
> >
> > On Mon, 5 Feb 2024 09:56:20 +0000
> > Matthew Chae <Matthew.Chae at axis.com> wrote:
> >
> > > Hi David,
> > >
> > > I'm sending an improved patch based on your comments.
> > >
> > > Not only does it not care about the PID_MAX value,
> > > it searches all the contents to be output to recognize the required column width
> > > and dynamically allocates the space for PID and PPID appropriately without creating a lot of empty space.
> > >
> > > Additionally, this patch still allows user names to be displayed up to 8 characters without truncation.
> > >
> > > Can you look through the attachment?
> >
> > Unfortunately the patch does not apply to current master.
> > How much would your patch add to the size? Can you bring it down to a
> > minimum?
> > See make baseline; apply the patch;make bloatcheck
> >
> > thanks
> >
> > > (0002-Allocate-PID-PPID-space-dynamically-in-top-command.patch)
> > >
> > > BR-Matthew Chae
> > > ________________________________
> > > From: David Laight <David.Laight at ACULAB.COM>
> > > Sent: Thursday, November 23, 2023 6:10 PM
> > > To: 'Denys Vlasenko' <vda.linux at googlemail.com>; Matthew Chae <Matthew.Chae at axis.com>
> > > Cc: busybox at busybox.net <busybox at busybox.net>; Christopher Wong <Christopher.Wong at axis.com>
> > > Subject: RE: fix large PID overflow their column in top command
> > >
> > > ...
> > > > + fp = xfopen_for_read("/proc/sys/kernel/pid_max");
> > > > + if (!fgets(pid_buf, PID_DIGITS_MAX + 1, fp)) {
> > > > ...
> > > > + if (strncmp(pid_buf, "32768", 5) == 0)
> > > > + pid_digits_num = 5;
> > > > + else
> > > > + pid_digits_num = PID_DIGITS_MAX;
> > > >
> > > > The logic above is not sound. Even if sysctl kernel.pid_max
> > > > is 32768, there can be already running processes with pids > 99999.
> > >
> > > It's also probably wrong for pretty much all other values.
> > >
> > > I'd just base the column width on strlen(pid_buf) with a minimum
> > > value of 5.
> > >
> > > It is unlikely that pid_max has been reduced - so column overflow
> > > it that case probably doesn't really matter.
> > >
> > > The more interesting case is really a system with a very large pid_max
> > > that has never run many processes.
> > > You don't really want lots of blank space.
> > >
> > > I can't remember whether top reads everything before doing any output?
> > > Since the output is sorted it probably almost always does.
> > > In which case it knows the column width it will need.
> > >
> > > I did post a patch a while back that enabled 'Irix mode'.
> > > (100% cpu is one cpu at 100%, not all cpus at 100%)
> > > Maybe I should dig it out again.
> > >
> > > David
> > >
> > > -
> > > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> > > Registration No: 1397386 (Wales)
> >
>
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