From: Andi Kleen <ak@linux.intel.com>
To: Vlastimil Babka <vbabka@suse.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
"David Hildenbrand (Arm)" <david@kernel.org>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Subject: Re: [PATCH v3] smaps: Report PMD page size for pure PMD mappings
Date: Wed, 4 Mar 2026 11:13:13 -0800 [thread overview]
Message-ID: <aaiESWyCYikx6s9e@tassilo> (raw)
In-Reply-To: <101ac423-252d-4ef8-a07c-34f5d59820f5@suse.com>
On Wed, Mar 04, 2026 at 06:29:09PM +0100, Vlastimil Babka wrote:
> Why do you keep not CCing people from v1/v2 discussions? David said that
> already on v2. It seems rather rude to me.
>
> On 3/3/26 9:15 PM, Andi Kleen wrote:
> > When a smaps mapping is only PMD mappings report the
> > PMD page size for MMUPageSize instead of the base page size.
> >
> > This is a revised version of an earlier patch that tried
> > to report multiple page sizes, but there were many objections
> > mainly centered around compatibility for mixed page size
> > reporting. This patch side steps all of this by
> > only handling the non mixed case in the simplest possible way.
> > It also avoids a problem introduced with v2 that page sizes
> > for mappings with no pages were incorrectly reported.
> >
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
>
> Will this be useful in practice or just confusing? There can be e.g.
It might have saved me some wasted time.
I found the current situation confusing!
> misaligned mappings, or other reasons why there won't be 100% THP
> coverage. This all or nothing value (IIUC) seems inferior to the
s/nothing/4K like what's there today/
Yes probably multiple page sizes would be better, but I'm not reopening
that discussion now.
> counters we have that say how much is pmd mapped, so I'm not really sure
> it's worth changing this.
The other counters still exist of course.
I don't see how there can be confusion if we report the correct page
size if the mapping is only that page size vs a page size that is not
used at all.
-Andi
next prev parent reply other threads:[~2026-03-04 19:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-03 20:15 Andi Kleen
2026-03-04 17:29 ` Vlastimil Babka
2026-03-04 19:13 ` Andi Kleen [this message]
2026-03-04 19:20 ` David Hildenbrand (Arm)
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