Date:   Tue, 19 Sep 2023 21:38:01 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 0/6] mm: page_alloc: freelist migratetype hygiene

On 19 Sep 2023, at 20:32, Mike Kravetz wrote:

> On 09/19/23 16:57, Zi Yan wrote:
>> On 19 Sep 2023, at 14:47, Mike Kravetz wrote:
>>
>>> On 09/19/23 02:49, Johannes Weiner wrote:
>>>> On Mon, Sep 18, 2023 at 10:40:37AM -0700, Mike Kravetz wrote:
>>>>> On 09/18/23 10:52, Johannes Weiner wrote:
>>>>>> On Mon, Sep 18, 2023 at 09:16:58AM +0200, Vlastimil Babka wrote:
>>>>>>> On 9/16/23 21:57, Mike Kravetz wrote:
>>>>>>>> On 09/15/23 10:16, Johannes Weiner wrote:
>>>>>>>>> On Thu, Sep 14, 2023 at 04:52:38PM -0700, Mike Kravetz wrote:
>>>
>>> Sorry for causing the confusion!
>>>
>>> When I originally saw the warnings pop up, I was running the above script
>>> as well as another that only allocated order 9 hugetlb pages:
>>>
>>> while true; do
>>> 	echo 2048 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
>>> 	echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
>>> done
>>>
>>> The warnings were actually triggered by allocations in this second script.
>>>
>>> However, when reporting the warnings I wanted to include the simplest
>>> way to recreate.  And, I noticed that that second script running in
>>> parallel was not required.  Again, sorry for the confusion!  Here is a
>>> warning triggered via the alloc_contig_range path only running the one
>>> script.
>>>
>>> [  107.275821] ------------[ cut here ]------------
>>> [  107.277001] page type is 0, passed migratetype is 1 (nr=512)
>>> [  107.278379] WARNING: CPU: 1 PID: 886 at mm/page_alloc.c:699 del_page_from_free_list+0x137/0x170
>>> [  107.280514] Modules linked in: rfkill ip6table_filter ip6_tables sunrpc snd_hda_codec_generic joydev 9p snd_hda_intel netfs snd_intel_dspcfg snd_hda_codec snd_hwdep 9pnet_virtio snd_hda_core snd_seq snd_seq_device 9pnet virtio_balloon snd_pcm snd_timer snd soundcore virtio_net net_failover failover virtio_console virtio_blk crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel serio_raw virtio_pci virtio virtio_pci_legacy_dev virtio_pci_modern_dev virtio_ring fuse
>>> [  107.291033] CPU: 1 PID: 886 Comm: bash Not tainted 6.6.0-rc2-next-20230919-dirty #35
>>> [  107.293000] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc37 04/01/2014
>>> [  107.295187] RIP: 0010:del_page_from_free_list+0x137/0x170
>>> [  107.296618] Code: c6 05 20 9b 35 01 01 e8 b7 fb ff ff 44 89 f1 44 89 e2 48 c7 c7 d8 ab 22 82 48 89 c6 b8 01 00 00 00 d3 e0 89 c1 e8 e9 99 df ff <0f> 0b e9 03 ff ff ff 48 c7 c6 10 ac 22 82 48 89 df e8 f3 e0 fc ff
>>> [  107.301236] RSP: 0018:ffffc90003ba7a70 EFLAGS: 00010086
>>> [  107.302535] RAX: 0000000000000000 RBX: ffffea0007ff8000 RCX: 0000000000000000
>>> [  107.304467] RDX: 0000000000000004 RSI: ffffffff8224e9de RDI: 00000000ffffffff
>>> [  107.306289] RBP: 00000000001ffe00 R08: 0000000000009ffb R09: 00000000ffffdfff
>>> [  107.308135] R10: 00000000ffffdfff R11: ffffffff824660e0 R12: 0000000000000001
>>> [  107.309956] R13: ffff88827fffcd80 R14: 0000000000000009 R15: 00000000001ffc00
>>> [  107.311839] FS:  00007fabb8cba740(0000) GS:ffff888277d00000(0000) knlGS:0000000000000000
>>> [  107.314695] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> [  107.316159] CR2: 00007f41ba01acf0 CR3: 0000000282ed4006 CR4: 0000000000370ee0
>>> [  107.317971] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> [  107.319783] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>> [  107.321575] Call Trace:
>>> [  107.322314]  <TASK>
>>> [  107.323002]  ? del_page_from_free_list+0x137/0x170
>>> [  107.324380]  ? __warn+0x7d/0x130
>>> [  107.325341]  ? del_page_from_free_list+0x137/0x170
>>> [  107.326627]  ? report_bug+0x18d/0x1c0
>>> [  107.327632]  ? prb_read_valid+0x17/0x20
>>> [  107.328711]  ? handle_bug+0x41/0x70
>>> [  107.329685]  ? exc_invalid_op+0x13/0x60
>>> [  107.330787]  ? asm_exc_invalid_op+0x16/0x20
>>> [  107.331937]  ? del_page_from_free_list+0x137/0x170
>>> [  107.333189]  __free_one_page+0x2ab/0x6f0
>>> [  107.334375]  free_pcppages_bulk+0x169/0x210
>>> [  107.335575]  drain_pages_zone+0x3f/0x50
>>> [  107.336691]  __drain_all_pages+0xe2/0x1e0
>>> [  107.337843]  alloc_contig_range+0x143/0x280
>>> [  107.339026]  alloc_contig_pages+0x210/0x270
>>> [  107.340200]  alloc_fresh_hugetlb_folio+0xa6/0x270
>>> [  107.341529]  alloc_pool_huge_page+0x7d/0x100
>>> [  107.342745]  set_max_huge_pages+0x162/0x340
>>> [  107.345059]  nr_hugepages_store_common+0x91/0xf0
>>> [  107.346329]  kernfs_fop_write_iter+0x108/0x1f0
>>> [  107.347547]  vfs_write+0x207/0x400
>>> [  107.348543]  ksys_write+0x63/0xe0
>>> [  107.349511]  do_syscall_64+0x37/0x90
>>> [  107.350543]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
>>> [  107.351940] RIP: 0033:0x7fabb8daee87
>>> [  107.352819] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
>>> [  107.356373] RSP: 002b:00007ffc02737478 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
>>> [  107.358103] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fabb8daee87
>>> [  107.359695] RDX: 0000000000000002 RSI: 000055fe584a1620 RDI: 0000000000000001
>>> [  107.361258] RBP: 000055fe584a1620 R08: 000000000000000a R09: 00007fabb8e460c0
>>> [  107.362842] R10: 00007fabb8e45fc0 R11: 0000000000000246 R12: 0000000000000002
>>> [  107.364385] R13: 00007fabb8e82520 R14: 0000000000000002 R15: 00007fabb8e82720
>>> [  107.365968]  </TASK>
>>> [  107.366534] ---[ end trace 0000000000000000 ]---
>>> [  121.542474] ------------[ cut here ]------------
>>>
>>> Perhaps that is another piece of information in that the warning can be
>>> triggered via both allocation paths.
>>>
>>> To be perfectly clear, here is what I did today:
>>> - built next-20230919.  It does not contain your series
>>>   	I could not recreate the issue.
>>> - Added your series and the patch to remove
>>>   VM_BUG_ON_PAGE(is_migrate_isolate(mt), page) from free_pcppages_bulk
>>> 	I could recreate the issue while running only the one script.
>>> 	The warning above is from that run.
>>> - Added this suggested patch from Zi
>>> 	diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> 	index 1400e674ab86..77a4aea31a7f 100644
>>> 	--- a/mm/page_alloc.c
>>> 	+++ b/mm/page_alloc.c
>>> 	@@ -1651,8 +1651,13 @@ static bool prep_move_freepages_block(struct zone *zone, struct page *page,
>>>  		end = pageblock_end_pfn(pfn) - 1;
>>>
>>>  		/* Do not cross zone boundaries */
>>> 	+#if 0
>>>  		if (!zone_spans_pfn(zone, start))
>>> 			start = zone->zone_start_pfn;
>>> 	+#else
>>> 	+	if (!zone_spans_pfn(zone, start))
>>> 	+		start = pfn;
>>> 	+#endif
>>> 	 	if (!zone_spans_pfn(zone, end))
>>> 	 		return false;
>>> 	I can still trigger warnings.
>>
>> OK. One thing to note is that the page type in the warning changed from
>> 5 (MIGRATE_ISOLATE) to 0 (MIGRATE_UNMOVABLE) with my suggested change.
>>
>
> Just to be really clear,
> - the 5 (MIGRATE_ISOLATE) warning was from the __alloc_pages call path.
> - the 0 (MIGRATE_UNMOVABLE) as above was from the alloc_contig_range call
>   path WITHOUT your change.
>
> I am guessing the difference here has more to do with the allocation path?
>
> I went back and reran focusing on the specific migrate type.
> Without your patch, and coming from the alloc_contig_range call path,
> I got two warnings of 'page type is 0, passed migratetype is 1' as above.
> With your patch I got one 'page type is 0, passed migratetype is 1'
> warning and one 'page type is 1, passed migratetype is 0' warning.
>
> I could be wrong, but I do not think your patch changes things.

Got it. Thanks for the clarification.
>
>>>
>>> One idea about recreating the issue is that it may have to do with size
>>> of my VM (16G) and the requested allocation sizes 4G.  However, I tried
>>> to really stress the allocations by increasing the number of hugetlb
>>> pages requested and that did not help.  I also noticed that I only seem
>>> to get two warnings and then they stop, even if I continue to run the
>>> script.
>>>
>>> Zi asked about my config, so it is attached.
>>
>> With your config, I still have no luck reproducing the issue. I will keep
>> trying. Thanks.
>>
>
> Perhaps try running both scripts in parallel?

Yes. It seems to do the trick.

> Adjust the number of hugetlb pages allocated to equal 25% of memory?

I am able to reproduce it with the script below:

while true; do
 echo 4 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages&
 echo 2048 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages&
 wait
 echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
 echo 0 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
done

I will look into the issue.

--
Best Regards,
Yan, Zi

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