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Message-ID: <9689bab0-fe44-40e4-a24d-72b778a521e6@arm.com> Date: Thu, 8 May 2025 15:00:42 +0100 From: Ryan Roberts <ryan.roberts@....com> To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Pasha Tatashin <pasha.tatashin@...een.com>, Andrew Morton <akpm@...ux-foundation.org>, Uladzislau Rezki <urezki@...il.com>, Christoph Hellwig <hch@...radead.org>, David Hildenbrand <david@...hat.com>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, Mark Rutland <mark.rutland@....com>, Anshuman Khandual <anshuman.khandual@....com>, Alexandre Ghiti <alexghiti@...osinc.com>, Kevin Brodsky <kevin.brodsky@....com> Cc: linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 00/11] Perf improvements for hugetlb and vmalloc on arm64 Hi Will, Just a bump on this; I believe it's had review by all the relavent folks (and has the R-b) tags. I was hoping to get this into v6.16, but getting nervous that time is running out to soak it in linux-next. Any chance you could consider pulling? Thanks, Ryan On 22/04/2025 09:18, Ryan Roberts wrote: > Hi All, > > This is v4 of a series to improve performance for hugetlb and vmalloc on arm64. > Although some of these patches are core-mm, advice from Andrew was to go via the > arm64 tree. All patches are now acked/reviewed by relevant maintainers so I > believe this should be good-to-go. > > The 2 key performance improvements are 1) enabling the use of contpte-mapped > blocks in the vmalloc space when appropriate (which reduces TLB pressure). There > were already hooks for this (used by powerpc) but they required some tidying and > extending for arm64. And 2) batching up barriers when modifying the vmalloc > address space for upto 30% reduction in time taken in vmalloc(). > > vmalloc() performance was measured using the test_vmalloc.ko module. Tested on > Apple M2 and Ampere Altra. Each test had loop count set to 500000 and the whole > test was repeated 10 times. > > legend: > - p: nr_pages (pages to allocate) > - h: use_huge (vmalloc() vs vmalloc_huge()) > - (I): statistically significant improvement (95% CI does not overlap) > - (R): statistically significant regression (95% CI does not overlap) > - measurements are times; smaller is better > > +--------------------------------------------------+-------------+-------------+ > | Benchmark | | | > | Result Class | Apple M2 | Ampere Alta | > +==================================================+=============+=============+ > | micromm/vmalloc | | | > | fix_align_alloc_test: p:1, h:0 (usec) | (I) -11.53% | -2.57% | > | fix_size_alloc_test: p:1, h:0 (usec) | 2.14% | 1.79% | > | fix_size_alloc_test: p:4, h:0 (usec) | (I) -9.93% | (I) -4.80% | > | fix_size_alloc_test: p:16, h:0 (usec) | (I) -25.07% | (I) -14.24% | > | fix_size_alloc_test: p:16, h:1 (usec) | (I) -14.07% | (R) 7.93% | > | fix_size_alloc_test: p:64, h:0 (usec) | (I) -29.43% | (I) -19.30% | > | fix_size_alloc_test: p:64, h:1 (usec) | (I) -16.39% | (R) 6.71% | > | fix_size_alloc_test: p:256, h:0 (usec) | (I) -31.46% | (I) -20.60% | > | fix_size_alloc_test: p:256, h:1 (usec) | (I) -16.58% | (R) 6.70% | > | fix_size_alloc_test: p:512, h:0 (usec) | (I) -31.96% | (I) -20.04% | > | fix_size_alloc_test: p:512, h:1 (usec) | 2.30% | 0.71% | > | full_fit_alloc_test: p:1, h:0 (usec) | -2.94% | 1.77% | > | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0 (usec) | -7.75% | 1.71% | > | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0 (usec) | -9.07% | (R) 2.34% | > | long_busy_list_alloc_test: p:1, h:0 (usec) | (I) -29.18% | (I) -17.91% | > | pcpu_alloc_test: p:1, h:0 (usec) | -14.71% | -3.14% | > | random_size_align_alloc_test: p:1, h:0 (usec) | (I) -11.08% | (I) -4.62% | > | random_size_alloc_test: p:1, h:0 (usec) | (I) -30.25% | (I) -17.95% | > | vm_map_ram_test: p:1, h:0 (usec) | 5.06% | (R) 6.63% | > +--------------------------------------------------+-------------+-------------+ > > So there are some nice improvements but also some regressions to explain: > > fix_size_alloc_test with h:1 and p:16,64,256 regress by ~6% on Altra. The > regression is actually introduced by enabling contpte-mapped 64K blocks in these > tests, and that regression is reduced (from about 8% if memory serves) by doing > the barrier batching. I don't have a definite conclusion on the root cause, but > I've ruled out the differences in the mapping paths in vmalloc. I strongly > believe this is likely due to the difference in the allocation path; 64K blocks > are not cached per-cpu so we have to go all the way to the buddy. I'm not sure > why this doesn't show up on M2 though. Regardless, I'm going to assert that it's > better to choose 16x reduction in TLB pressure vs 6% on the vmalloc allocation > call duration. > > Changes since v3 [3] > ==================== > - Applied R-bs (thanks all!) > - Renamed set_ptes_anysz() -> __set_ptes_anysz() (Catalin) > - Renamed ptep_get_and_clear_anysz() -> __ptep_get_and_clear_anysz() (Catalin) > - Only set TIF_LAZY_MMU_PENDING if not already set to avoid atomic ops (Catalin) > - Fix commet typos (Anshuman) > - Fix build warnings when PMD is folded (buildbot) > - Reverse xmas tree for variables in __page_table_check_p[mu]ds_set() (Pasha) > > Changes since v2 [2] > ==================== > - Removed the new arch_update_kernel_mappings_[begin|end]() API > - Switches to arch_[enter|leave]_lazy_mmu_mode() instead for barrier batching > - Removed clean up to avoid barriers for invalid or user mappings > > Changes since v1 [1] > ==================== > - Split out the fixes into their own series > - Added Rbs from Anshuman - Thanks! > - Added patch to clean up the methods by which huge_pte size is determined > - Added "#ifndef __PAGETABLE_PMD_FOLDED" around PUD_SIZE in > flush_hugetlb_tlb_range() > - Renamed ___set_ptes() -> set_ptes_anysz() > - Renamed ___ptep_get_and_clear() -> ptep_get_and_clear_anysz() > - Fixed typos in commit logs > - Refactored pXd_valid_not_user() for better reuse > - Removed TIF_KMAP_UPDATE_PENDING after concluding that single flag is sufficent > - Concluded the extra isb() in __switch_to() is not required > - Only call arch_update_kernel_mappings_[begin|end]() for kernel mappings > > Applies on top of v6.15-rc3. All mm selftests run and no regressions observed. > > [1] https://lore.kernel.org/all/20250205151003.88959-1-ryan.roberts@arm.com/ > [2] https://lore.kernel.org/all/20250217140809.1702789-1-ryan.roberts@arm.com/ > [3] https://lore.kernel.org/all/20250304150444.3788920-1-ryan.roberts@arm.com/ > > Thanks, > Ryan > > Ryan Roberts (11): > arm64: hugetlb: Cleanup huge_pte size discovery mechanisms > arm64: hugetlb: Refine tlb maintenance scope > mm/page_table_check: Batch-check pmds/puds just like ptes > arm64/mm: Refactor __set_ptes() and __ptep_get_and_clear() > arm64: hugetlb: Use __set_ptes_anysz() and > __ptep_get_and_clear_anysz() > arm64/mm: Hoist barriers out of set_ptes_anysz() loop > mm/vmalloc: Warn on improper use of vunmap_range() > mm/vmalloc: Gracefully unmap huge ptes > arm64/mm: Support huge pte-mapped pages in vmap > mm/vmalloc: Enter lazy mmu mode while manipulating vmalloc ptes > arm64/mm: Batch barriers when updating kernel mappings > > arch/arm64/include/asm/hugetlb.h | 29 ++-- > arch/arm64/include/asm/pgtable.h | 209 +++++++++++++++++++-------- > arch/arm64/include/asm/thread_info.h | 2 + > arch/arm64/include/asm/vmalloc.h | 45 ++++++ > arch/arm64/kernel/process.c | 9 +- > arch/arm64/mm/hugetlbpage.c | 73 ++++------ > include/linux/page_table_check.h | 30 ++-- > include/linux/vmalloc.h | 8 + > mm/page_table_check.c | 34 +++-- > mm/vmalloc.c | 40 ++++- > 10 files changed, 329 insertions(+), 150 deletions(-) > > -- > 2.43.0 >
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