Messages in this thread | | | Date | Tue, 9 Apr 2024 16:45:12 +0200 | Subject | Re: [PATCH v2 0/4] Speed up boot with faster linear map creation | From | David Hildenbrand <> |
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On 09.04.24 16:39, Ryan Roberts wrote: > On 09/04/2024 15:29, David Hildenbrand wrote: >> On 09.04.24 16:13, Ryan Roberts wrote: >>> On 09/04/2024 12:51, David Hildenbrand wrote: >>>> On 09.04.24 13:29, David Hildenbrand wrote: >>>>> On 09.04.24 13:22, David Hildenbrand wrote: >>>>>> On 09.04.24 12:13, Itaru Kitayama wrote: >>>>>>> >>>>>>> >>>>>>>> On Apr 9, 2024, at 19:04, Ryan Roberts <ryan.roberts@arm.com> wrote: >>>>>>>> >>>>>>>> On 09/04/2024 01:10, Itaru Kitayama wrote: >>>>>>>>> Hi Ryan, >>>>>>>>> >>>>>>>>>> On Apr 8, 2024, at 16:30, Ryan Roberts <ryan.roberts@arm.com> wrote: >>>>>>>>>> >>>>>>>>>> On 06/04/2024 11:31, Itaru Kitayama wrote: >>>>>>>>>>> Hi Ryan, >>>>>>>>>>> >>>>>>>>>>> On Sat, Apr 06, 2024 at 09:32:34AM +0100, Ryan Roberts wrote: >>>>>>>>>>>> Hi Itaru, >>>>>>>>>>>> >>>>>>>>>>>> On 05/04/2024 08:39, Itaru Kitayama wrote: >>>>>>>>>>>>> On Thu, Apr 04, 2024 at 03:33:04PM +0100, Ryan Roberts wrote: >>>>>>>>>>>>>> Hi All, >>>>>>>>>>>>>> >>>>>>>>>>>>>> It turns out that creating the linear map can take a significant >>>>>>>>>>>>>> proportion of >>>>>>>>>>>>>> the total boot time, especially when rodata=full. And most of the >>>>>>>>>>>>>> time is spent >>>>>>>>>>>>>> waiting on superfluous tlb invalidation and memory barriers. This >>>>>>>>>>>>>> series reworks >>>>>>>>>>>>>> the kernel pgtable generation code to significantly reduce the number >>>>>>>>>>>>>> of those >>>>>>>>>>>>>> TLBIs, ISBs and DSBs. See each patch for details. >>>>>>>>>>>>>> >>>>>>>>>>>>>> The below shows the execution time of map_mem() across a couple of >>>>>>>>>>>>>> different >>>>>>>>>>>>>> systems with different RAM configurations. We measure after applying >>>>>>>>>>>>>> each patch >>>>>>>>>>>>>> and show the improvement relative to base (v6.9-rc2): >>>>>>>>>>>>>> >>>>>>>>>>>>>> | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere >>>>>>>>>>>>>> Altra >>>>>>>>>>>>>> | VM, 16G | VM, 64G | VM, 256G | Metal, >>>>>>>>>>>>>> 512G >>>>>>>>>>>>>> ---------------|-------------|-------------|-------------|------------- >>>>>>>>>>>>>> | ms (%) | ms (%) | ms (%) | >>>>>>>>>>>>>> ms (%) >>>>>>>>>>>>>> ---------------|-------------|-------------|-------------|------------- >>>>>>>>>>>>>> base | 153 (0%) | 2227 (0%) | 8798 (0%) | 17442 >>>>>>>>>>>>>> (0%) >>>>>>>>>>>>>> no-cont-remap | 77 (-49%) | 431 (-81%) | 1727 (-80%) | 3796 >>>>>>>>>>>>>> (-78%) >>>>>>>>>>>>>> batch-barriers | 13 (-92%) | 162 (-93%) | 655 (-93%) | 1656 >>>>>>>>>>>>>> (-91%) >>>>>>>>>>>>>> no-alloc-remap | 11 (-93%) | 109 (-95%) | 449 (-95%) | 1257 >>>>>>>>>>>>>> (-93%) >>>>>>>>>>>>>> lazy-unmap | 6 (-96%) | 61 (-97%) | 257 (-97%) | 838 >>>>>>>>>>>>>> (-95%) >>>>>>>>>>>>>> >>>>>>>>>>>>>> This series applies on top of v6.9-rc2. All mm selftests pass. I've >>>>>>>>>>>>>> compile and >>>>>>>>>>>>>> boot tested various PAGE_SIZE and VA size configs. >>>>>>>>>>>>>> >>>>>>>>>>>>>> --- >>>>>>>>>>>>>> >>>>>>>>>>>>>> Changes since v1 [1] >>>>>>>>>>>>>> ==================== >>>>>>>>>>>>>> >>>>>>>>>>>>>> - Added Tested-by tags (thanks to Eric and Itaru) >>>>>>>>>>>>>> - Renamed ___set_pte() -> __set_pte_nosync() (per Ard) >>>>>>>>>>>>>> - Reordered patches (biggest impact & least controversial first) >>>>>>>>>>>>>> - Reordered alloc/map/unmap functions in mmu.c to aid reader >>>>>>>>>>>>>> - pte_clear() -> __pte_clear() in clear_fixmap_nosync() >>>>>>>>>>>>>> - Reverted generic p4d_index() which caused x86 build error. >>>>>>>>>>>>>> Replaced with >>>>>>>>>>>>>> unconditional p4d_index() define under arm64. >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> [1] >>>>>>>>>>>>>> https://lore.kernel.org/linux-arm-kernel/20240326101448.3453626-1-ryan.roberts@arm.com/<https://lore.kernel.org/linux-arm-kernel/20240326101448.3453626-1-ryan.roberts@arm.com/> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>> Ryan >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Ryan Roberts (4): >>>>>>>>>>>>>> arm64: mm: Don't remap pgtables per-cont(pte|pmd) block >>>>>>>>>>>>>> arm64: mm: Batch dsb and isb when populating pgtables >>>>>>>>>>>>>> arm64: mm: Don't remap pgtables for allocate vs populate >>>>>>>>>>>>>> arm64: mm: Lazily clear pte table mappings from fixmap >>>>>>>>>>>>>> >>>>>>>>>>>>>> arch/arm64/include/asm/fixmap.h | 5 +- >>>>>>>>>>>>>> arch/arm64/include/asm/mmu.h | 8 + >>>>>>>>>>>>>> arch/arm64/include/asm/pgtable.h | 13 +- >>>>>>>>>>>>>> arch/arm64/kernel/cpufeature.c | 10 +- >>>>>>>>>>>>>> arch/arm64/mm/fixmap.c | 11 + >>>>>>>>>>>>>> arch/arm64/mm/mmu.c | 377 +++++++++++++++++++++++-------- >>>>>>>>>>>>>> 6 files changed, 319 insertions(+), 105 deletions(-) >>>>>>>>>>>>>> >>>>>>>>>>>>>> -- >>>>>>>>>>>>>> 2.25.1 >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> I've build and boot tested the v2 on FVP, base is taken from your >>>>>>>>>>>>> linux-rr repo. Running run_vmtests.sh on v2 left some gup longterm not >>>>>>>>>>>>> oks, would you take a look at it? The mm ksefltests used is from your >>>>>>>>>>>>> linux-rr repo too. >>>>>>>>>>>> >>>>>>>>>>>> Thanks for taking a look at this. >>>>>>>>>>>> >>>>>>>>>>>> I can't reproduce your issue unfortunately; steps as follows on Apple >>>>>>>>>>>> M2 VM: >>>>>>>>>>>> >>>>>>>>>>>> Config: arm64 defconfig + the following: >>>>>>>>>>>> >>>>>>>>>>>> # Squashfs for snaps, xfs for large file folios. >>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_LZ4 >>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_LZO >>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_XZ >>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_ZSTD >>>>>>>>>>>> ./scripts/config --enable CONFIG_XFS_FS >>>>>>>>>>>> >>>>>>>>>>>> # For general mm debug. >>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM >>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_MAPLE_TREE >>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_RB >>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_PGFLAGS >>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_PGTABLE >>>>>>>>>>>> ./scripts/config --enable CONFIG_PAGE_TABLE_CHECK >>>>>>>>>>>> >>>>>>>>>>>> # For mm selftests. >>>>>>>>>>>> ./scripts/config --enable CONFIG_USERFAULTFD >>>>>>>>>>>> ./scripts/config --enable CONFIG_TEST_VMALLOC >>>>>>>>>>>> ./scripts/config --enable CONFIG_GUP_TEST >>>>>>>>>>>> >>>>>>>>>>>> Running on VM with 12G memory, split across 2 (emulated) NUMA nodes >>>>>>>>>>>> (needed by >>>>>>>>>>>> some mm selftests), with kernel command line to reserve hugetlbs and >>>>>>>>>>>> other >>>>>>>>>>>> features required by some mm selftests: >>>>>>>>>>>> >>>>>>>>>>>> " >>>>>>>>>>>> transparent_hugepage=madvise earlycon root=/dev/vda2 secretmem.enable >>>>>>>>>>>> hugepagesz=1G hugepages=0:2,1:2 hugepagesz=32M hugepages=0:2,1:2 >>>>>>>>>>>> default_hugepagesz=2M hugepages=0:64,1:64 hugepagesz=64K >>>>>>>>>>>> hugepages=0:2,1:2 >>>>>>>>>>>> " >>>>>>>>>>>> >>>>>>>>>>>> Ubuntu userspace running off XFS rootfs. Build and run mm selftests >>>>>>>>>>>> from same >>>>>>>>>>>> git tree. >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Although I don't think any of this config should make a difference to >>>>>>>>>>>> gup_longterm. >>>>>>>>>>>> >>>>>>>>>>>> Looks like your errors are all "ftruncate() failed". I've seen this >>>>>>>>>>>> problem on >>>>>>>>>>>> our CI system. There it is due to running the tests from NFS file >>>>>>>>>>>> system. What >>>>>>>>>>>> filesystem are you using? Perhaps you are sharing into the FVP using >>>>>>>>>>>> 9p? That >>>>>>>>>>>> might also be problematic. >>>>>>>>>>> >>>>>>>>>>> That was it. This time I booted up the kernel including your series on >>>>>>>>>>> QEMU on my M1 and executed the gup_longterm program without the ftruncate >>>>>>>>>>> failures. When testing your kernel on FVP, I was executing the script >>>>>>>>>>> from the FVP's host filesystem using 9p. >>>>>>>>>> >>>>>>>>>> I'm not sure exactly what the root cause is. Perhaps there isn't enough >>>>>>>>>> space on >>>>>>>>>> the disk? It might be worth enhancing the error log to provide the >>>>>>>>>> errno in >>>>>>>>>> tools/testing/selftests/mm/gup_longterm.c. >>>>>>>>>> >>>>>>>>> >>>>>>>>> Attached is the strace’d gup_longterm executiong log on your >>>>>>>>> pgtable-boot-speedup-v2 kernel. >>>>>>>> >>>>>>>> Sorry are you saying that it only fails with the pgtable-boot-speedup-v2 >>>>>>>> patch >>>>>>>> set applied? I thought we previously concluded that it was independent of >>>>>>>> that? >>>>>>>> I was under the impression that it was filesystem related and not something >>>>>>>> that >>>>>>>> I was planning to investigate. >>>>>>> >>>>>>> No, irrespective of the kernel, if using 9p on FVP the test program fails. >>>>>>> It is indeed 9p filesystem related, as I switched to using NFS all the >>>>>>> issues are gone. >>>>>> >>>>>> Did it never work on 9p? If so, we might have to SKIP that test. >>>>>> >>>>>> openat(AT_FDCWD, "gup_longterm.c_tmpfile_BLboOt", O_RDWR|O_CREAT|O_EXCL, >>>>>> 0600) = 3 >>>>>> unlinkat(AT_FDCWD, "gup_longterm.c_tmpfile_BLboOt", 0) = 0 >>>>>> fstatfs(3, 0xffffe505a840) = -1 EOPNOTSUPP (Operation not >>>>>> supported) >>>>>> ftruncate(3, 4096) = -1 ENOENT (No such file or >>>>>> directory) >>>>> >>>>> Note: I'm wondering if the unlinkat here is the problem that makes >>>>> ftruncate() with 9p result in weird errors (e.g., the hypervisor >>>>> unlinked the file and cannot reopen it for the fstatfs/ftruncate. ... >>>>> which gives us weird errors here). >>>>> >>>>> Then, we should lookup the fs type in run_with_local_tmpfile() before >>>>> the unlink() and simply skip the test if it is 9p. >>>> >>>> The unlink with 9p most certainly was a known issue in the past: >>>> >>>> https://gitlab.com/qemu-project/qemu/-/issues/103 >>>> >>>> Maybe it's still an issue with older hypervisors (QEMU?)? Or it was never >>>> completely resolved? >>> >>> I believe Itaru is running on FVP (Fixed Virtual Platform - "fast model" - >>> Arm's architecture emulator). So QEMU won't be involved here. The FVP emulates >>> a 9p device, so perhaps the bug is in there. >> >> Very likely. >> >>> >>> Note that I see lots of "fallocate() failed" failures in gup_longterm when >>> running on our CI system. This is a completely different setup; Real HW with >>> Linux running bare metal using an NFS rootfs. I'm not sure if this is related. >>> Logs show it failing consistently for the "tmpfile" and "local tmpfile" test >>> configs. I also see a couple of these fails in the cow tests. >> >> What is the fallocate() errno you are getting? strace log would help (to see if >> statfs also fails already)! Likely a similar NFS issue. > > Unfortunately this is a system I don't have access to. I've requested some of > this triage to be done, but its fairly low priority unfortunately.
To work around these BUGs (?) elsewhere, we could simply skip the test if get_fs_type() is not able to detect the FS type. Likely that's an early indicator that the unlink() messed something up.
.. doesn't feel right, though.
-- Cheers,
David / dhildenb
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