Re: [PATCH, RESEND2] getrusage: fill ru_maxrss value

On Wed, 17 Dec 2008 21:03:27 +0900 (JST)
KOSAKI Motohiro [off-list ref] wrote:

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This patch makes ->ru_maxrss value in struct rusage filled accordingly to
rss hiwater mark. This struct is filled as a parameter to
getrusage syscall. ->ru_maxrss value is set to pages which might be correct
as "time" application converts it to KBs.

Why?
if kernel convert to KB, glibc don't need any change.

Where exactly glibc is working with this as KBs? I can't find that place.

I looked into sources of time util and maxrss is showed this way:
fprintf (fp, "%lu", ptok ((UL) resp->ru.ru_maxrss));
ptok() actually does pages_to_KB conversion. If we convert to KB in
kernel, this code must be changed.

Ah, you talked about /usr/bin/time? sorry, I misunderstood a bit.
Why time need number of pages?

In general, getrusage()::ru_maxrss is bsd compatibility feature.
as far as possible, the same syscall spec is better.
and bsd use KB unit.

Oh you are right. Now I searched it in FreeBSD kernel. They goes like this:
rss = pgtok(vmspace_resident_count(vm));
if (ru->ru_maxrss < rss)
	ru->ru_maxrss = rss;

Seems pretty reasonable to stick with the same behavior. Then I really
do not understand why /usr/bin/time does the conversion.
FreeBSD /usr/bin/time is very different and much simpler and (of
course) does not do this conversion.

So I suggest to change the patch to fill KB instead of pages and
change /usr/bin/time to not do the conversion. What do you think?

if time command has reasonable reason, I can agree current design.
but is there?