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Message-ID: <CAA1CXcACBMTPN-y4-J6wgiTf90ia5576xOJKFULnvGPCt56U6w@mail.gmail.com> Date: Fri, 14 Feb 2025 18:47:13 -0700 From: Nico Pache <npache@...hat.com> To: Dev Jain <dev.jain@....com> Cc: akpm@...ux-foundation.org, david@...hat.com, willy@...radead.org, kirill.shutemov@...ux.intel.com, ryan.roberts@....com, anshuman.khandual@....com, catalin.marinas@....com, cl@...two.org, vbabka@...e.cz, mhocko@...e.com, apopple@...dia.com, dave.hansen@...ux.intel.com, will@...nel.org, baohua@...nel.org, jack@...e.cz, srivatsa@...il.mit.edu, haowenchao22@...il.com, hughd@...gle.com, aneesh.kumar@...nel.org, yang@...amperecomputing.com, peterx@...hat.com, ioworker0@...il.com, wangkefeng.wang@...wei.com, ziy@...dia.com, jglisse@...gle.com, surenb@...gle.com, vishal.moola@...il.com, zokeefe@...gle.com, zhengqi.arch@...edance.com, jhubbard@...dia.com, 21cnbao@...il.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2 00/17] khugepaged: Asynchronous mTHP collapse Hi Dev, I tried to run your kernel to get some performance numbers out of it, but ran into the following issue while running my defer-mthp-test.sh workload. [ 297.393032] ===================================== [ 297.393618] WARNING: bad unlock balance detected! [ 297.394201] 6.14.0-rc2mthpDEV #2 Not tainted [ 297.394732] ------------------------------------- [ 297.395421] khugepaged/111 is trying to release lock (&mm->mmap_lock) at: [ 297.396509] [<ffffffff947cb76a>] khugepaged+0x23a/0xb40 [ 297.397205] but there are no more locks to release! [ 297.397865] [ 297.397865] other info that might help us debug this: [ 297.398684] no locks held by khugepaged/111. [ 297.399155] [ 297.399155] stack backtrace: [ 297.399591] CPU: 10 UID: 0 PID: 111 Comm: khugepaged Not tainted 6.14.0-rc2mthpDEV #2 [ 297.399593] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 [ 297.399595] Call Trace: [ 297.399599] <TASK> [ 297.399602] dump_stack_lvl+0x6e/0xa0 [ 297.399607] ? khugepaged+0x23a/0xb40 [ 297.399610] print_unlock_imbalance_bug.part.0+0xfb/0x110 [ 297.399612] ? khugepaged+0x23a/0xb40 [ 297.399614] lock_release+0x283/0x3f0 [ 297.399620] up_read+0x1b/0x30 [ 297.399622] khugepaged+0x23a/0xb40 [ 297.399631] ? __pfx_khugepaged+0x10/0x10 [ 297.399633] kthread+0xf2/0x240 [ 297.399636] ? __pfx_kthread+0x10/0x10 [ 297.399638] ret_from_fork+0x34/0x50 [ 297.399640] ? __pfx_kthread+0x10/0x10 [ 297.399642] ret_from_fork_asm+0x1a/0x30 [ 297.399649] </TASK> [ 297.505555] ------------[ cut here ]------------ [ 297.506044] DEBUG_RWSEMS_WARN_ON(tmp < 0): count = 0xffffffffffffff00, magic = 0xffff8c6e03bc1f88, owner = 0x1, curr 0xffff8c6e0eccb700, list empty [ 297.507362] WARNING: CPU: 8 PID: 1946 at kernel/locking/rwsem.c:1346 __up_read+0x1ba/0x220 [ 297.508220] Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rfkill nf_tables intel_rapl_msr intel_rapl_common kvm_amd iTCO_wdt intel_pmc_bxt iTCO_vendor_support kvm i2c_i801 i2c_smbus lpc_ich virtio_net net_failover failover virtio_balloon joydev fuse loop nfnetlink zram xfs polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 sha256_ssse3 virtio_console virtio_blk sha1_ssse3 serio_raw qemu_fw_cfg [ 297.513474] CPU: 8 UID: 0 PID: 1946 Comm: thp_test Not tainted 6.14.0-rc2mthpDEV #2 [ 297.514314] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 [ 297.515265] RIP: 0010:__up_read+0x1ba/0x220 [ 297.515756] Code: c6 78 8b e1 95 48 c7 c7 88 0e d3 95 48 39 c2 48 c7 c2 be 39 e4 95 48 c7 c0 29 8b e1 95 48 0f 44 c2 48 8b 13 50 e8 e6 44 f5 ff <0f> 0b 58 e9 20 ff ff ff 48 8b 57 60 48 8d 47 60 4c 8b 47 08 c6 05 [ 297.517659] RSP: 0018:ffffa8a943533ac8 EFLAGS: 00010282 [ 297.518209] RAX: 0000000000000000 RBX: ffff8c6e03bc1f88 RCX: 0000000000000000 [ 297.518884] RDX: ffff8c7366ff0980 RSI: ffff8c7366fe1a80 RDI: ffff8c7366fe1a80 [ 297.519577] RBP: ffffa8a943533b58 R08: 0000000000000000 R09: 0000000000000001 [ 297.520272] R10: 0000000000000000 R11: 0770076d07650720 R12: ffffa8a943533b10 [ 297.520949] R13: ffff8c6e03bc1f88 R14: ffffa8a943533b58 R15: ffffa8a943533b10 [ 297.521651] FS: 00007f24de01b740(0000) GS:ffff8c7366e00000(0000) knlGS:0000000000000000 [ 297.522425] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 297.522990] CR2: 0000000a7ffef000 CR3: 000000010d9d6000 CR4: 0000000000750ef0 [ 297.523799] PKRU: 55555554 [ 297.524100] Call Trace: [ 297.524367] <TASK> [ 297.524597] ? __warn.cold+0xb7/0x151 [ 297.525072] ? __up_read+0x1ba/0x220 [ 297.525442] ? report_bug+0xff/0x140 [ 297.525804] ? console_unlock+0x9d/0x150 [ 297.526233] ? handle_bug+0x58/0x90 [ 297.526590] ? exc_invalid_op+0x17/0x70 [ 297.526993] ? asm_exc_invalid_op+0x1a/0x20 [ 297.527420] ? __up_read+0x1ba/0x220 [ 297.527783] ? __up_read+0x1ba/0x220 [ 297.528160] vms_complete_munmap_vmas+0x19c/0x1f0 [ 297.528628] do_vmi_align_munmap+0x20a/0x280 [ 297.529069] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.529552] do_vmi_munmap+0xd0/0x190 [ 297.529920] __vm_munmap+0xb1/0x1b0 [ 297.530293] __x64_sys_munmap+0x1b/0x30 [ 297.530677] do_syscall_64+0x95/0x180 [ 297.531058] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.531534] ? lockdep_hardirqs_on_prepare+0xdb/0x190 [ 297.532167] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.532640] ? syscall_exit_to_user_mode+0x97/0x290 [ 297.533226] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.533701] ? do_syscall_64+0xa1/0x180 [ 297.534097] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.534587] ? lockdep_hardirqs_on_prepare+0xdb/0x190 [ 297.535129] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.535603] ? syscall_exit_to_user_mode+0x97/0x290 [ 297.536092] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.536568] ? do_syscall_64+0xa1/0x180 [ 297.536954] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.537444] ? lockdep_hardirqs_on_prepare+0xdb/0x190 [ 297.537936] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.538524] ? syscall_exit_to_user_mode+0x97/0x290 [ 297.539044] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.539526] ? do_syscall_64+0xa1/0x180 [ 297.539931] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.540597] ? do_user_addr_fault+0x5a9/0x8a0 [ 297.541102] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.541580] ? trace_hardirqs_off+0x4b/0xc0 [ 297.542011] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.542488] ? lockdep_hardirqs_on_prepare+0xdb/0x190 [ 297.542991] ? srso_alias_return_thunk+0x5/0xfbef5 [ 297.543466] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 297.543960] RIP: 0033:0x7f24de1367eb [ 297.544344] Code: 73 01 c3 48 8b 0d 2d f6 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d fd f5 0c 00 f7 d8 64 89 01 48 [ 297.546074] RSP: 002b:00007ffc7bb2e2b8 EFLAGS: 00000206 ORIG_RAX: 000000000000000b [ 297.546796] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f24de1367eb [ 297.547488] RDX: 0000000080000000 RSI: 0000000080000000 RDI: 0000000480000000 [ 297.548182] RBP: 00007ffc7bb2e390 R08: 0000000000000064 R09: 00000000fffffffe [ 297.548884] R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000006 [ 297.549594] R13: 0000000000000000 R14: 00007f24de258000 R15: 0000000000403e00 [ 297.550292] </TASK> [ 297.550530] irq event stamp: 64417291 [ 297.550903] hardirqs last enabled at (64417291): [<ffffffff94749232>] seqcount_lockdep_reader_access+0x82/0x90 [ 297.551859] hardirqs last disabled at (64417290): [<ffffffff947491fe>] seqcount_lockdep_reader_access+0x4e/0x90 [ 297.552810] softirqs last enabled at (64413640): [<ffffffff943bf3c2>] __irq_exit_rcu+0xe2/0x100 [ 297.553654] softirqs last disabled at (64413627): [<ffffffff943bf3c2>] __irq_exit_rcu+0xe2/0x100 [ 297.554504] ---[ end trace 0000000000000000 ]--- On Tue, Feb 11, 2025 at 4:13 AM Dev Jain <dev.jain@....com> wrote: > > This patchset extends khugepaged from collapsing only PMD-sized THPs to > collapsing anonymous mTHPs. > > mTHPs were introduced in the kernel to improve memory management by allocating > chunks of larger memory, so as to reduce number of page faults, TLB misses (due > to TLB coalescing), reduce length of LRU lists, etc. However, the mTHP property > is often lost due to CoW, swap-in/out, and when the kernel just cannot find > enough physically contiguous memory to allocate on fault. Henceforth, there is a > need to regain mTHPs in the system asynchronously. This work is an attempt in > this direction, starting with anonymous folios. > > In the fault handler, we select the THP order in a greedy manner; the same has > been used here, along with the same sysfs interface to control the order of > collapse. In contrast to PMD-collapse, we (hopefully) get rid of the mmap_write_lock(). > > --------------------------------------------------------- > Testing > --------------------------------------------------------- > > The set has been build tested on x86_64. > For Aarch64, > 1. mm-selftests: No regressions. > 2. Analyzing with tools/mm/thpmaps on different userspace programs mapping > aligned VMAs of a large size, faulting in basepages/mTHPs (according to sysfs), > and then madvise()'ing the VMA, khugepaged is able to 100% collapse the VMAs. > > This patchset is rebased on mm-unstable (4637fa5d47a49c977116321cc575ea22215df22d). > > v1->v2: > - Handle VMAs less than PMD size (patches 12-15) > - Do not add mTHP into deferred split queue > - Drop lock optimization and collapse mTHP under mmap_write_lock() > - Define policy on what to do when we encounter a folio order larger than > the order we are scanning for > - Prevent the creep problem by enforcing tunable simplification > - Update Documentation > - Drop patch 12 from v1 updating selftest w.r.t the creep problem > - Drop patch 1 from v1 > > v1: > https://lore.kernel.org/all/20241216165105.56185-1-dev.jain@arm.com/ > > Dev Jain (17): > khugepaged: Generalize alloc_charge_folio() > khugepaged: Generalize hugepage_vma_revalidate() > khugepaged: Generalize __collapse_huge_page_swapin() > khugepaged: Generalize __collapse_huge_page_isolate() > khugepaged: Generalize __collapse_huge_page_copy() > khugepaged: Abstract PMD-THP collapse > khugepaged: Scan PTEs order-wise > khugepaged: Introduce vma_collapse_anon_folio() > khugepaged: Define collapse policy if a larger folio is already mapped > khugepaged: Exit early on fully-mapped aligned mTHP > khugepaged: Enable sysfs to control order of collapse > khugepaged: Enable variable-sized VMA collapse > khugepaged: Lock all VMAs mapping the PTE table > khugepaged: Reset scan address to correct alignment > khugepaged: Delay cond_resched() > khugepaged: Implement strict policy for mTHP collapse > Documentation: transhuge: Define khugepaged mTHP collapse policy > > Documentation/admin-guide/mm/transhuge.rst | 49 +- > include/linux/huge_mm.h | 2 + > mm/huge_memory.c | 4 + > mm/khugepaged.c | 603 ++++++++++++++++----- > 4 files changed, 511 insertions(+), 147 deletions(-) > > -- > 2.30.2 >
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