linux-kernel - Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

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Date:   Mon, 13 Nov 2017 18:45:01 +0000
From:   Roman Gushchin <guro@...com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
CC:     Dave Hansen <dave.hansen@...el.com>, <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>, <kernel-team@...com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: show stats for non-default hugepage sizes in
 /proc/meminfo

On Mon, Nov 13, 2017 at 10:30:10AM -0800, Mike Kravetz wrote:
> On 11/13/2017 10:17 AM, Dave Hansen wrote:
> > On 11/13/2017 10:11 AM, Roman Gushchin wrote:
> >> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
> >>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> >>>> To solve this problem, let's display stats for all hugepage sizes.
> >>>> To provide the backward compatibility let's save the existing format
> >>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
> >>>
> >>> Is there something keeping you from using the sysfs version of this
> >>> information?
> >>
> >> Just answered the same question to Michal.
> >>
> >> In two words: it would be nice to have a high-level overview of
> >> memory usage in the system in /proc/meminfo. 
> > 
> > I don't think it's worth cluttering up meminfo for this, imnho.
> 
> I tend to agree that it would be better not to add additional huge page
> sizes here.  It may not seem too intrusive to (potentially) add one extra
> set of entries for GB huge pages on x86.  However, other architectures
> such as powerpc or sparc have several several huge pages sizes that could
> potentially be added here as well.  Although, in practice one does tend
> to use a single huge pages size.  If you change the default huge page
> size, then those entries will be in /proc/meminfo.

I do agree that it might add some unnecessary verbosity if these sizes
are not used, but if they are, this information is super-useful.
So, might be a conditional printing will work here?

Or, at least, some total counter, e.g. how much memory is consumed
by hugetlb pages?

Thanks!