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: 24+ 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 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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.