From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Juan Yescas <jyescas@google.com>
Cc: "David Hildenbrand (Arm)" <david@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
open list <linux-kernel@vger.kernel.org>,
"open list:MEMORY MANAGEMENT - CORE" <linux-mm@kvack.org>,
android-mm@google.com, fvdl@google.com, tkjos@google.com,
minchan@google.com, dskiba@google.com
Subject: Re: [RFC PATCH 00/16] Page Alloc Hogger
Date: Fri, 31 Jul 2026 13:40:42 +0100 [thread overview]
Message-ID: <amyWt8XYlQJRJXmg@lucifer> (raw)
In-Reply-To: <CAJDx_rjNhiS+J9eDkQxPF6B=jJ-Evr-M7NNeS_QcG7XWNDoEYQ@mail.gmail.com>
On Tue, Jul 28, 2026 at 05:36:03PM -0700, Juan Yescas wrote:
> On Tue, Jul 28, 2026 at 12:29 PM David Hildenbrand (Arm)
> <david@kernel.org> wrote:
> >
> > On 7/23/26 09:47, Juan Yescas wrote:
> > > This patch series introduces the Page Alloc Hogger. The Page Alloc Hogger
> > > allows you to allocate memory pages from specific nodes, zones, migration
> > > types, and orders directly via debugfs. This provides key benefits for
> > > testing and debugging:
> >
> > Would it be feasible to carry this as an OOT debugging module? Would a lot of
> > symbols be missing to achieve that?
> >
>
> Thanks David for the comment.
>
> The only symbol that would be needed to have this module as OOT is
> "migratetype_names".
Hmm I could have sworn I replied to this :)
Anyway, I don't think there's any need to export this. It's not like we're going
to radically rename them, and you'd probably have to update your module anyway
if we added a new migratetype.
So this being wholly contained in a module with no core changes seems the best
way?
Cheers, Lorenzo
>
> However, although this module was originally designed to debug CMA
> issues, it can be
> easily used to debug issues in kswapd, direct reclaims, OOM killer,
> etc. We could even
> use this module to add kunit test cases.
>
> Let's take for example this case. We want to allocate Unmovable memory and check
> that the allocation came from Movable, as per the buddy allocator
> fallback mechanism.
> How can we do that in user space?
>
> $ cat /proc/pagetypeinfo
> Page block order: 9
> Pages per block: 512
>
> Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
> Node 0, zone DMA, type Unmovable 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type Movable 1 1 1 0 1 1 2 2 1 3 732
> Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 1 7
> Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type Unmovable 13 7 0 1 0 0 1 0 1 0 0
> Node 0, zone Normal, type Movable 1 1 1 1 1 1 1 0 1 1 1221
> Node 0, zone Normal, type Reclaimable 1 0 0 0 0 0 1 0 0 1 0
> Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 1 7
> Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
>
> // Allocate Unmovable memory (note that there are NO Unmovable pages,
> so the allocation will fall back from Movable)
> $ echo 1221 > /sys/kernel/debug/mm/node-0/zone-Normal/order-10/migrate-Unmovable/nr_pages_allocs
>
> $ cat /proc/pagetypeinfo
> Page block order: 9
> Pages per block: 512
>
> Free pages count per migrate type at order 0 1 2
> 3 4 5 6 7 8 9 10
> Node 0, zone DMA, type Unmovable 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type Movable 1 1 1
> 0 1 1 2 2 1 3 701
> Node 0, zone DMA, type Reclaimable 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type HighAtomic 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type CMA 0 0 0
> 0 0 0 0 0 0 1 31
> Node 0, zone DMA, type Isolate 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type Unmovable 1 0 0
> 1 1 1 1 1 1 0 0
> Node 0, zone Normal, type Movable 1 0 1
> 1 1 1 1 1 1 1 7
> Node 0, zone Normal, type Reclaimable 0 1 0
> 0 1 0 0 0 1 0 0
> Node 0, zone Normal, type HighAtomic 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type CMA 0 0 0
> 0 0 0 0 0 0 1 7
> Node 0, zone Normal, type Isolate 0 0 0
> 0 0 0 0 0 0 0 0
>
> Number of blocks type Unmovable Movable Reclaimable
> HighAtomic CMA Isolate
> Node 0, zone DMA 14 1458 0
> 0 64 0
> Node 0, zone Normal 2440 102 2
> 0 16 0
>
> // Now we want to test that Reclaimable memory allocations fall back
> from ZONE_DMA and Migrate Movable
>
> $ echo 600 > /sys/kernel/debug/mm/node-0/zone-Normal/order-10/migrate-Reclaimable/nr_pages_allocs
> # cat /proc/pagetypeinfo
> Page block order: 9
> Pages per block: 512
>
> Free pages count per migrate type at order 0 1 2
> 3 4 5 6 7 8 9 10
> Node 0, zone DMA, type Unmovable 0 0 0
> 0 0 1 1 0 0 1 0
> Node 0, zone DMA, type Movable 1 1 1
> 0 1 1 2 2 1 3 99
> Node 0, zone DMA, type Reclaimable 1 0 0
> 1 0 0 1 0 1 1 0
> Node 0, zone DMA, type HighAtomic 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type CMA 0 0 0
> 0 0 0 0 0 0 1 31
> Node 0, zone DMA, type Isolate 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type Unmovable 1 0 0
> 1 1 1 1 1 1 0 0
> Node 0, zone Normal, type Movable 0 0 0
> 1 0 0 1 0 1 0 7
> Node 0, zone Normal, type Reclaimable 0 1 0
> 0 1 0 0 0 1 0 0
> Node 0, zone Normal, type HighAtomic 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type CMA 0 0 0
> 0 0 0 0 0 0 1 7
> Node 0, zone Normal, type Isolate 0 0 0
> 0 0 0 0 0 0 0 0
>
> Number of blocks type Unmovable Movable Reclaimable
> HighAtomic CMA Isolate
> Node 0, zone DMA 16 254 1202
> 0 64 0
> Node 0, zone Normal 2440 102 2
> 0 16 0
>
> // Now, we want to free all the MIGRATE_UNMOVABLE allocations and
> sleep 1 second for every
> // allocation and see how the pages return to the MIGRATE_UNMOVABLE bucket:
>
> for i in `seq 1 1221`; do echo $i > /sys/kernel/debug/mm/free; sleep 10; done
>
> // in another console
>
> watch cat /proc/pagetypeinfo
> 2026-07-29 00:28:49
>
> Page block order: 9
> Pages per block: 512
>
> Free pages count per migrate type at order 0 1 2
> 3 4 5 6 7 8 9 10
> Node 0, zone DMA, type Unmovable 0 0 0
> 0 0 1 1 0 0 1 0
> Node 0, zone DMA, type Movable 1 1 1
> 0 1 1 2 2 1 3 99
> Node 0, zone DMA, type Reclaimable 1 0 0
> 1 0 0 1 0 1 1 0
> Node 0, zone DMA, type HighAtomic 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone DMA, type CMA 0 0 0
> 0 0 0 0 0 0 1 31
> Node 0, zone DMA, type Isolate 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type Unmovable 1 0 0
> 1 1 1 1 1 1 0 698
> Node 0, zone Normal, type Movable 1 0 0
> 1 0 0 0 0 1 0 7
> Node 0, zone Normal, type Reclaimable 0 1 0
> 0 1 0 0 0 1 0 0
> Node 0, zone Normal, type HighAtomic 0 0 0
> 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type CMA 0 0 0
> 0 0 0 0 0 0 1 7
> Node 0, zone Normal, type Isolate 0 0 0
> 0 0 0 0 0 0 0 0
>
> Number of blocks type Unmovable Movable Reclaimable
> HighAtomic CMA Isolate
> Node 0, zone DMA 16 254 1202
> 0 64 0
> Node 0, zone Normal 2440 102 2
> 0 16 0
>
> Achieving the same result in a user program is not as straightforward.
>
> The Page Alloc Hogger gives us the flexibility to allocate from any
> valid memory we desire.
>
> As I mentioned before, it allows us to test/check/analyze/generate:
>
> - kwapd triggers
> - direct reclaims
> - OOM killer
> - generate page fragmentation using simple scripts instead of complex programs
>
> Greetigns
>
> Juan
>
>
> > --
> > Cheers,
> >
> > David
--
Cheers, Lorenzo
next prev parent reply other threads:[~2026-07-31 12:41 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-23 7:47 [RFC PATCH 00/16] Page Alloc Hogger Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 01/16] mm: Page Alloc Hogger module Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 02/16] mm: Define structs for allocation requests and store allocations Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 03/16] mm: Define the caches for the structs req_alloc and page_alloc Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 04/16] mm: Define function to create a dir for each online node Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 05/16] mm: Define function to create a dir for populated zone Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 06/16] mm: Define function to create a dir for each page order Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 07/16] mm: Define function to create a dir for each migrate type Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 08/16] mm: Define function that creates the "nr_pages_allocs" file Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 09/16] mm: Read the nr_pages_allocs value given by user Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 10/16] mm: Set the selected zone in gfp_t flags Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 11/16] mm: Sets the migrate type " Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 12/16] mm: Define the make_alloc() function Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 13/16] mm: Create the file asociated with an allocation Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 14/16] mm: Free pages, remove files and clean cache when one alloc fails Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 15/16] mm: Create the "free" file to release the previously allocated pages Juan Yescas
2026-07-23 7:47 ` [RFC PATCH 16/16] mm: Release resources when the page alloc hogger module exits Juan Yescas
2026-07-28 19:29 ` [RFC PATCH 00/16] Page Alloc Hogger David Hildenbrand (Arm)
2026-07-29 0:36 ` Juan Yescas
2026-07-30 7:50 ` Lorenzo Stoakes (ARM)
2026-07-31 15:32 ` Juan Yescas
2026-07-31 15:55 ` Lorenzo Stoakes (ARM)
2026-07-31 17:52 ` Juan Yescas
2026-07-31 12:40 ` Lorenzo Stoakes (ARM) [this message]
2026-07-31 12:42 ` Lorenzo Stoakes (ARM)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=amyWt8XYlQJRJXmg@lucifer \
--to=ljs@kernel.org \
--cc=Liam.Howlett@oracle.com \
--cc=akpm@linux-foundation.org \
--cc=android-mm@google.com \
--cc=david@kernel.org \
--cc=dskiba@google.com \
--cc=fvdl@google.com \
--cc=jyescas@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lorenzo.stoakes@oracle.com \
--cc=mhocko@suse.com \
--cc=minchan@google.com \
--cc=rppt@kernel.org \
--cc=surenb@google.com \
--cc=tkjos@google.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox