Messages in this thread | | | Date | Tue, 9 Apr 2024 13:29:31 +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 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.
-- Cheers,
David / dhildenb
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