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: >>>>>> >>>>>> With the patch below applied, a slightly different workload triggers the >>>>>> following warnings. It seems related, and appears to go away when >>>>>> reverting the series. >>>>>> >>>>>> [ 331.595382] ------------[ cut here ]------------ >>>>>> [ 331.596665] page type is 5, passed migratetype is 1 (nr=512) >>>>>> [ 331.598121] WARNING: CPU: 2 PID: 935 at mm/page_alloc.c:662 expand+0x1c9/0x200 >>>>> >>>>> Initially I thought this demonstrates the possible race I was suggesting in >>>>> reply to 6/6. But, assuming you have CONFIG_CMA, page type 5 is cma and we >>>>> are trying to get a MOVABLE page from a CMA page block, which is something >>>>> that's normally done and the pageblock stays CMA. So yeah if the warnings >>>>> are to stay, they need to handle this case. Maybe the same can happen with >>>>> HIGHATOMIC blocks? >> >> Ok, the CMA thing gave me pause because Mike's pagetypeinfo didn't >> show any CMA pages. >> >> 5 is actually MIGRATE_ISOLATE - see the double use of 3 for PCPTYPES >> and HIGHATOMIC. >> >>>> This means we have an order-10 page where one half is MOVABLE and the >>>> other is CMA. >> >> This means the scenario is different: >> >> We get a MAX_ORDER page off the MOVABLE freelist. The removal checks >> that the first pageblock is indeed MOVABLE. During the expand, the >> second pageblock turns out to be of type MIGRATE_ISOLATE. >> >> The page allocator wouldn't have merged those types. It triggers a bit >> too fast to be a race condition. >> >> It appears that MIGRATE_ISOLATE is simply set on the tail pageblock >> while the head is on the list, and then stranded there. >> >> Could this be an issue in the page_isolation code? Maybe a range >> rounding error? >> >> Zi Yan, does this ring a bell for you? >> >> I don't quite see how my patches could have caused this. But AFAICS we >> also didn't have warnings for this scenario so it could be an old bug. >> >>>> Mike, could you describe the workload that is triggering this? >>> >>> This 'slightly different workload' is actually a slightly different >>> environment. Sorry for mis-speaking! The slight difference is that this >>> environment does not use the 'alloc hugetlb gigantic pages from CMA' >>> (hugetlb_cma) feature that triggered the previous issue. >>> >>> This is still on a 16G VM. Kernel command line here is: >>> "BOOT_IMAGE=(hd0,msdos1)/vmlinuz-6.6.0-rc1-next-20230913+ >>> root=UUID=49c13301-2555-44dc-847b-caabe1d62bdf ro console=tty0 >>> console=ttyS0,115200 audit=0 selinux=0 transparent_hugepage=always >>> hugetlb_free_vmemmap=on" >>> >>> The workload is just running this script: >>> while true; do >>> echo 4 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages >>> echo 4 > /sys/kernel/mm/hugepages/hugepages-1048576kB/demote >>> echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages >>> done >>> >>>> >>>> Does this reproduce instantly and reliably? >>>> >>> >>> It is not 'instant' but will reproduce fairly reliably within a minute >>> or so. >>> >>> Note that the 'echo 4 > .../hugepages-1048576kB/nr_hugepages' is going >>> to end up calling alloc_contig_pages -> alloc_contig_range. Those pages >>> will eventually be freed via __free_pages(folio, 9). >> >> No luck reproducing this yet, but I have a question. In that crash >> stack trace, the expand() is called via this: >> >> [ 331.645847] get_page_from_freelist+0x3ed/0x1040 >> [ 331.646837] ? prepare_alloc_pages.constprop.0+0x197/0x1b0 >> [ 331.647977] __alloc_pages+0xec/0x240 >> [ 331.648783] alloc_buddy_hugetlb_folio.isra.0+0x6a/0x150 >> [ 331.649912] __alloc_fresh_hugetlb_folio+0x157/0x230 >> [ 331.650938] alloc_pool_huge_folio+0xad/0x110 >> [ 331.651909] set_max_huge_pages+0x17d/0x390 >> >> I don't see an __alloc_fresh_hugetlb_folio() in my tree. Only >> alloc_fresh_hugetlb_folio(), which has this: >> >> if (hstate_is_gigantic(h)) >> folio = alloc_gigantic_folio(h, gfp_mask, nid, nmask); >> else >> folio = alloc_buddy_hugetlb_folio(h, gfp_mask, >> nid, nmask, node_alloc_noretry); >> >> where gigantic is defined as the order exceeding MAX_ORDER, which >> should be the case for 1G pages on x86. >> >> So the crashing stack must be from a 2M allocation, no? I'm confused >> how that could happen with the above test case. > > 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. > > 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. -- Best Regards, Yan, Zi
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