Re: [PATCH] getrusage: fill ru_maxrss value

From: Michael Kerrisk
Date: Tue Dec 02 2008 - 11:50:59 EST

On Tue, Dec 2, 2008 at 11:05 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> On 12/02, Jiri Pirko wrote:
>> Based on the patch previously posted by Frank Mayhar:
>> Changed to do not panic and to set the value properly. Also made some
>> modifications as Oleg suggested. maxrss value is set to pages as "time"
>> application converts it co KBs.
>> This patch enables "time" application to show maxresident value
>> correctly.
> I believe the changelog could be a bit more descriptive ;)
> And I think the patch needs more CCs. (Hugh and Michael cc'ed).

Thanks Oleg.

Jiri: linux-api@ should also be CCed on API changes; see
Documentation/SubmitChecklist and

> What about exec? Should we preserve signal_struct->maxrss, or should
> we reset it? I don't know what is the right behaviour, but imho it
> should be consistent with task_mem()/xacct_add_tsk(). And since
> bprm_mm_init() does not copy ->hiwater_xxx, perhaps we should reset.
> Or we should change the exec_mmap() path to preserve ->hiwater_xxx,
> I dunno.
>> Note that even without this patch applied there is a race between two
>> parallel update_hiwater_rss() callers.
>> [...snip...]
>> @@ -1051,6 +1051,8 @@ NORET_TYPE void do_exit(long code)
>> if (tsk->mm) {
>> update_hiwater_rss(tsk->mm);
>> update_hiwater_vm(tsk->mm);
>> +
>> + tsk->signal->maxrss = tsk->mm->hiwater_rss;
> Yes. But still it is not good the patch adds new racy calls
> (k_getrusage() too). And in fact I think this code in do_exit()
> should die, and we can update signal->maxrss in exit_mm().
> Unless I missed something, the "if (tsk->mm) {}" code in
> do_exit() is not needed because xacct_add_tsk() is not right
> anyway. What we imho need is get_mm_hiwater_xxx(), can be
> also used by task_mm().
> I'll send the patch a bit later, then we can tweak this patch.
> Do you agree?
> (just in case, I don't mean that mm/ uses update_hiwater_xxx()
> "safely", afaics try_to_unmap can race with unmap_region
> for example, but still).
> Oleg.

Michael Kerrisk
Linux man-pages maintainer;
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