| Message ID | 20240202080756.1453939-1-ryan.roberts@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Transparent Contiguous PTEs for User Mappings | expand |
On Fri, Feb 02, 2024 at 08:07:31AM +0000, Ryan Roberts wrote: > Hi All, Hi Ryan, I assume this is the same as your 'features/granule_perf/contpte-lkml_v' branch on https://gitlab.arm.com/linux-arm/linux-rr/ I've taken a quick look, and I have a few initial/superficial comments before digging into the detail on the important changes. > Patch Layout > ============ > > In this version, I've split the patches to better show each optimization: > > - 1-2: mm prep: misc code and docs cleanups I'm not confident enough to comment on patch 2, but these look reasonable to me. > - 3-8: mm,arm,arm64,powerpc,x86 prep: Replace pte_next_pfn() with more > general pte_advance_pfn() These look fine to me. > - 9-18: arm64 prep: Refactor ptep helpers into new layer The result of patches 9-17 looks good to me, but the intermediate stages where some functions are converted is a bit odd, and it's a bit painful for review since you need to skip ahead a few patches to see the end result to tell that the conversions are consistent and complete. IMO it'd be easier for review if that were three patches: 1) Convert READ_ONCE() -> ptep_get() 2) Convert set_pte_at() -> set_ptes() 3) All the "New layer" renames and addition of the trivial wrappers Patch 18 looks fine to me. > - 19: functional contpte implementation > - 20-25: various optimizations on top of the contpte implementation I'll try to dig into these over the next few days. Mark.
On 08/02/2024 17:34, Mark Rutland wrote: > On Fri, Feb 02, 2024 at 08:07:31AM +0000, Ryan Roberts wrote: >> Hi All, > > Hi Ryan, > > I assume this is the same as your 'features/granule_perf/contpte-lkml_v' branch > on https://gitlab.arm.com/linux-arm/linux-rr/ Yep - great detective work! features/granule_perf/contpte-lkml_v5 corresponds exactly to what I posted with all the dependencies in place. > > I've taken a quick look, and I have a few initial/superficial comments before > digging into the detail on the important changes. Thanks for doing this! > >> Patch Layout >> ============ >> >> In this version, I've split the patches to better show each optimization: >> >> - 1-2: mm prep: misc code and docs cleanups > > I'm not confident enough to comment on patch 2, but these look reasonable to > me. Thanks. David has acked patch 2 already so I think we are good there. > >> - 3-8: mm,arm,arm64,powerpc,x86 prep: Replace pte_next_pfn() with more >> general pte_advance_pfn() > > These look fine to me. Thanks! > >> - 9-18: arm64 prep: Refactor ptep helpers into new layer > > The result of patches 9-17 looks good to me, but the intermediate stages where > some functions are converted is a bit odd, and it's a bit painful for review > since you need to skip ahead a few patches to see the end result to tell that > the conversions are consistent and complete. > > IMO it'd be easier for review if that were three patches: > > 1) Convert READ_ONCE() -> ptep_get() > 2) Convert set_pte_at() -> set_ptes() > 3) All the "New layer" renames and addition of the trivial wrappers Yep that makes sense. I'll start prepping that today. I'll hold off reposting until I have your comments on 19-25. I'm also hoping that David will repost the zap series today so that it can get into mm-unstable by mid-next week. Then I'll repost on top of that, hopefully by end of next week, folding in all your comments. This should give planty of time to soak in linux-next. Thanks, Ryan > > Patch 18 looks fine to me. > >> - 19: functional contpte implementation >> - 20-25: various optimizations on top of the contpte implementation > > I'll try to dig into these over the next few days. > > Mark.
>> 1) Convert READ_ONCE() -> ptep_get() >> 2) Convert set_pte_at() -> set_ptes() >> 3) All the "New layer" renames and addition of the trivial wrappers > > Yep that makes sense. I'll start prepping that today. I'll hold off reposting > until I have your comments on 19-25. I'm also hoping that David will repost the > zap series today so that it can get into mm-unstable by mid-next week. Then I'll > repost on top of that, hopefully by end of next week, folding in all your > comments. This should give planty of time to soak in linux-next. Just sent out v2. Will review this series (early) next week. Have a great weekend!
On 09/02/2024 22:16, David Hildenbrand wrote: >>> 1) Convert READ_ONCE() -> ptep_get() >>> 2) Convert set_pte_at() -> set_ptes() >>> 3) All the "New layer" renames and addition of the trivial wrappers >> >> Yep that makes sense. I'll start prepping that today. I'll hold off reposting >> until I have your comments on 19-25. I'm also hoping that David will repost the >> zap series today so that it can get into mm-unstable by mid-next week. Then I'll >> repost on top of that, hopefully by end of next week, folding in all your >> comments. This should give planty of time to soak in linux-next. > > Just sent out v2. Will review this series (early) next week. > > Have a great weekend! Cheers, David - you too! >
Hi All, This is a series to opportunistically and transparently use contpte mappings (set the contiguous bit in ptes) for user memory when those mappings meet the requirements. The change benefits arm64, but there is some minor refactoring for x86 and powerpc to enable its integration with core-mm. It is part of a wider effort to improve performance by allocating and mapping variable-sized blocks of memory (folios). One aim is for the 4K kernel to approach the performance of the 16K kernel, but without breaking compatibility and without the associated increase in memory. Another aim is to benefit the 16K and 64K kernels by enabling 2M THP, since this is the contpte size for those kernels. We have good performance data that demonstrates both aims are being met (see below). Of course this is only one half of the change. We require the mapped physical memory to be the correct size and alignment for this to actually be useful (i.e. 64K for 4K pages, or 2M for 16K/64K pages). Fortunately folios are solving this problem for us. Filesystems that support it (XFS, AFS, EROFS, tmpfs, ...) will allocate large folios up to the PMD size today, and more filesystems are coming. And for anonymous memory, "multi-size THP" is now upstream. Patch Layout ============ In this version, I've split the patches to better show each optimization: - 1-2: mm prep: misc code and docs cleanups - 3-8: mm,arm,arm64,powerpc,x86 prep: Replace pte_next_pfn() with more general pte_advance_pfn() - 9-18: arm64 prep: Refactor ptep helpers into new layer - 19: functional contpte implementation - 20-25: various optimizations on top of the contpte implementation Testing ======= I've tested this series on both Ampere Altra (bare metal) and Apple M2 (VM): - mm selftests (inc new tests written for multi-size THP); no regressions - Speedometer Java script benchmark in Chromium web browser; no issues - Kernel compilation; no issues - Various tests under high memory pressure with swap enabled; no issues Performance =========== High Level Use Cases ~~~~~~~~~~~~~~~~~~~~ First some high level use cases (kernel compilation and speedometer JavaScript benchmarks). These are running on Ampere Altra (I've seen similar improvements on Android/Pixel 6). baseline: mm-unstable (mTHP switched off) mTHP: + enable 16K, 32K, 64K mTHP sizes "always" mTHP + contpte: + this series mTHP + contpte + exefolio: + patch at [5], which series supports Kernel Compilation with -j8 (negative is faster): | kernel | real-time | kern-time | user-time | |---------------------------|-----------|-----------|-----------| | baseline | 0.0% | 0.0% | 0.0% | | mTHP | -5.0% | -39.1% | -0.7% | | mTHP + contpte | -6.0% | -41.4% | -1.5% | | mTHP + contpte + exefolio | -7.8% | -43.1% | -3.4% | Kernel Compilation with -j80 (negative is faster): | kernel | real-time | kern-time | user-time | |---------------------------|-----------|-----------|-----------| | baseline | 0.0% | 0.0% | 0.0% | | mTHP | -5.0% | -36.6% | -0.6% | | mTHP + contpte | -6.1% | -38.2% | -1.6% | | mTHP + contpte + exefolio | -7.4% | -39.2% | -3.2% | Speedometer (positive is faster): | kernel | runs_per_min | |:--------------------------|--------------| | baseline | 0.0% | | mTHP | 1.5% | | mTHP + contpte | 3.2% | | mTHP + contpte + exefolio | 4.5% | Micro Benchmarks ~~~~~~~~~~~~~~~~ The following microbenchmarks are intended to demonstrate the performance of fork() and munmap() do not regress. I'm showing results for order-0 (4K) mappings, and for order-9 (2M) PTE-mapped THP. Thanks to David for sharing his benchmarks. baseline: mm-unstable + batch fork [6] and zap [7] series contpte-basic: + patches 0-19; functional contpte implementation contpte-batch: + patches 20-23; implement new batched APIs contpte-inline: + patch 24; __always_inline to help compiler contpte-fold: + patch 25; fold contpte mapping when sensible Primary platform is Ampere Altra bare metal. I'm also showing results for M2 VM (on top of MacOS) for reference, although experience suggests this might not be the most reliable for performance numbers of this sort: | FORK | order-0 | order-9 | | Ampere Altra |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 2.7% | 0.0% | 0.2% | | contpte-basic | 6.3% | 1.4% | 1948.7% | 0.2% | | contpte-batch | 7.6% | 2.0% | -1.9% | 0.4% | | contpte-inline | 3.6% | 1.5% | -1.0% | 0.2% | | contpte-fold | 4.6% | 2.1% | -1.8% | 0.2% | | MUNMAP | order-0 | order-9 | | Ampere Altra |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 0.5% | 0.0% | 0.3% | | contpte-basic | 1.8% | 0.3% | 1104.8% | 0.1% | | contpte-batch | -0.3% | 0.4% | 2.7% | 0.1% | | contpte-inline | -0.1% | 0.6% | 0.9% | 0.1% | | contpte-fold | 0.1% | 0.6% | 0.8% | 0.1% | | FORK | order-0 | order-9 | | Apple M2 VM |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 1.4% | 0.0% | 0.8% | | contpte-basic | 6.8% | 1.2% | 469.4% | 1.4% | | contpte-batch | -7.7% | 2.0% | -8.9% | 0.7% | | contpte-inline | -6.0% | 2.1% | -6.0% | 2.0% | | contpte-fold | 5.9% | 1.4% | -6.4% | 1.4% | | MUNMAP | order-0 | order-9 | | Apple M2 VM |------------------------|------------------------| | (pte-map) | mean | stdev | mean | stdev | |----------------|------------|-----------|------------|-----------| | baseline | 0.0% | 0.6% | 0.0% | 0.4% | | contpte-basic | 1.6% | 0.6% | 233.6% | 0.7% | | contpte-batch | 1.9% | 0.3% | -3.9% | 0.4% | | contpte-inline | 2.2% | 0.8% | -1.6% | 0.9% | | contpte-fold | 1.5% | 0.7% | -1.7% | 0.7% | Misc ~~~~ John Hubbard at Nvidia has indicated dramatic 10x performance improvements for some workloads at [8], when using 64K base page kernel. --- I'd really like to get this into v6.9; I've spoken with Catalin and he is happy for this to go via the mm-unstable branch, once suitably acked by arm64 folks. That makes most sense because the series depends on some changes from David at [6] and [7], which in turn apply on top of mm-unstable as of a few days ago (d162e170f118). Changes since v4 [4] ==================== - Rebased onto David's generic fork [6] and zap [8] batching work - I had an implementation similar to this prior to v4, but ditched it because I couldn't make it reliably provide a speedup; David succeeded. - roughly speaking, a few functions get renamed compared to v4: - pte_batch_remaining() -> pte_batch_hint() - set_wrprotects() -> wrprotect_ptes() - clear_ptes() -> [get_and_]clear_full_ptes() - Had to convert pte_next_pfn() to pte_advance_pfn() - Integration into core-mm is simpler because most has been done by David's work - Reworked patches to better show the progression from basic implementation to the various optimizations. - Removed the 'full' flag that I added to set_ptes() and set_wrprotects() in v4: I've been able to make up most of the performance in other ways, so this keeps the interface simpler. - Simplified contpte_set_ptes(nr > 1): Observed that set_ptes(nr > 1) is only called for ptes that are initially not present. So updated the spec to require that, and no longer need to check if any ptes are initially present when applying a contpte mapping. Changes since v3 [3] ==================== - Added v3#1 to batch set_ptes() when splitting a huge pmd to ptes; avoids need to fold contpte blocks for perf improvement - Separated the clear_ptes() fast path into its own inline function (Alistair) - Reworked core-mm changes to copy_present_ptes() and zap_pte_range() to remove overhead when memory is all order-0 folios (for arm64 and !arm64) - Significant optimization of arm64 backend fork operations (set_ptes_full() and set_wrprotects()) to ensure no regression when memory is order-0 folios. - fixed local variable declarations to be reverse xmas tree. - Added documentation for the new backend APIs (pte_batch_remaining(), set_ptes_full(), clear_ptes(), ptep_set_wrprotects()) - Renamed tlb_get_guaranteed_space() -> tlb_reserve_space() and pass requested number of slots. Avoids allocating memory when not needed; perf improvement. Changes since v2 [2] ==================== - Removed contpte_ptep_get_and_clear_full() optimisation for exit() (v2#14), and replaced with a batch-clearing approach using a new arch helper, clear_ptes() (v3#2 and v3#15) (Alistair and Barry) - (v2#1 / v3#1) - Fixed folio refcounting so that refcount >= mapcount always (DavidH) - Reworked batch demarcation to avoid pte_pgprot() (DavidH) - Reverted return semantic of copy_present_page() and instead fix it up in copy_present_ptes() (Alistair) - Removed page_cont_mapped_vaddr() and replaced with simpler logic (Alistair) - Made batch accounting clearer in copy_pte_range() (Alistair) - (v2#12 / v3#13) - Renamed contpte_fold() -> contpte_convert() and hoisted setting/ clearing CONT_PTE bit to higher level (Alistair) Changes since v1 [1] ==================== - Export contpte_* symbols so that modules can continue to call inline functions (e.g. ptep_get) which may now call the contpte_* functions (thanks to JohnH) - Use pte_valid() instead of pte_present() where sensible (thanks to Catalin) - Factor out (pte_valid() && pte_cont()) into new pte_valid_cont() helper (thanks to Catalin) - Fixed bug in contpte_ptep_set_access_flags() where TLBIs were missed (thanks to Catalin) - Added ARM64_CONTPTE expert Kconfig (enabled by default) (thanks to Anshuman) - Simplified contpte_ptep_get_and_clear_full() - Improved various code comments [1] https://lore.kernel.org/linux-arm-kernel/20230622144210.2623299-1-ryan.roberts@arm.com/ [2] https://lore.kernel.org/linux-arm-kernel/20231115163018.1303287-1-ryan.roberts@arm.com/ [3] https://lore.kernel.org/linux-arm-kernel/20231204105440.61448-1-ryan.roberts@arm.com/ [4] https://lore.kernel.org/lkml/20231218105100.172635-1-ryan.roberts@arm.com/ [5] https://lore.kernel.org/lkml/08c16f7d-f3b3-4f22-9acc-da943f647dc3@arm.com/ [6] https://lore.kernel.org/lkml/20240129124649.189745-1-david@redhat.com/ [7] https://lore.kernel.org/lkml/20240129143221.263763-1-david@redhat.com/ [8] https://lore.kernel.org/linux-mm/c507308d-bdd4-5f9e-d4ff-e96e4520be85@nvidia.com/ Thanks, Ryan Ryan Roberts (25): mm: Clarify the spec for set_ptes() mm: thp: Batch-collapse PMD with set_ptes() mm: Make pte_next_pfn() a wrapper around pte_advance_pfn() arm/mm: Convert pte_next_pfn() to pte_advance_pfn() arm64/mm: Convert pte_next_pfn() to pte_advance_pfn() powerpc/mm: Convert pte_next_pfn() to pte_advance_pfn() x86/mm: Convert pte_next_pfn() to pte_advance_pfn() mm: Remove pte_next_pfn() and replace with pte_advance_pfn() arm64/mm: set_pte(): New layer to manage contig bit arm64/mm: set_ptes()/set_pte_at(): New layer to manage contig bit arm64/mm: pte_clear(): New layer to manage contig bit arm64/mm: ptep_get_and_clear(): New layer to manage contig bit arm64/mm: ptep_test_and_clear_young(): New layer to manage contig bit arm64/mm: ptep_clear_flush_young(): New layer to manage contig bit arm64/mm: ptep_set_wrprotect(): New layer to manage contig bit arm64/mm: ptep_set_access_flags(): New layer to manage contig bit arm64/mm: ptep_get(): New layer to manage contig bit arm64/mm: Split __flush_tlb_range() to elide trailing DSB arm64/mm: Wire up PTE_CONT for user mappings arm64/mm: Implement new wrprotect_ptes() batch API arm64/mm: Implement new [get_and_]clear_full_ptes() batch APIs mm: Add pte_batch_hint() to reduce scanning in folio_pte_batch() arm64/mm: Implement pte_batch_hint() arm64/mm: __always_inline to improve fork() perf arm64/mm: Automatically fold contpte mappings arch/arm/mm/mmu.c | 2 +- arch/arm64/Kconfig | 9 + arch/arm64/include/asm/pgtable.h | 404 ++++++++++++++++++++++++++---- arch/arm64/include/asm/tlbflush.h | 13 +- arch/arm64/kernel/efi.c | 4 +- arch/arm64/kernel/mte.c | 2 +- arch/arm64/kvm/guest.c | 2 +- arch/arm64/mm/Makefile | 1 + arch/arm64/mm/contpte.c | 399 +++++++++++++++++++++++++++++ arch/arm64/mm/fault.c | 12 +- arch/arm64/mm/fixmap.c | 4 +- arch/arm64/mm/hugetlbpage.c | 40 +-- arch/arm64/mm/kasan_init.c | 6 +- arch/arm64/mm/mmu.c | 16 +- arch/arm64/mm/pageattr.c | 6 +- arch/arm64/mm/trans_pgd.c | 6 +- arch/powerpc/mm/pgtable.c | 2 +- arch/x86/include/asm/pgtable.h | 8 +- include/linux/pgtable.h | 29 ++- mm/huge_memory.c | 58 +++-- mm/memory.c | 20 +- 21 files changed, 906 insertions(+), 137 deletions(-) create mode 100644 arch/arm64/mm/contpte.c -- 2.25.1