While reviewing Alexandre Ghiti's "riscv: tlb flush improvements" series[1], I noticed that most TLB flush functions end up as a call to local_flush_tlb_all() when SMP is disabled. This series resolves that, and also optimizes the scenario where SMP is enabled but only one CPU is present or online. Along the way, I realized that we should be using single-ASID flushes wherever possible, so I implemented that as well. Here are some numbers from D1 (with SMP disabled) which show the performance impact: v6.8-rc6 + riscv/fixes + riscv/for-next: System Benchmarks Partial Index BASELINE RESULT INDEX Execl Throughput 43.0 223.5 52.0 File Copy 1024 bufsize 2000 maxblocks 3960.0 62563.4 158.0 File Copy 256 bufsize 500 maxblocks 1655.0 17869.2 108.0 File Copy 4096 bufsize 8000 maxblocks 5800.0 164915.1 284.3 Pipe Throughput 12440.0 161368.5 129.7 Pipe-based Context Switching 4000.0 22247.1 55.6 Process Creation 126.0 546.9 43.4 Shell Scripts (1 concurrent) 42.4 599.6 141.4 Shell Scripts (16 concurrent) --- 39.3 --- Shell Scripts (8 concurrent) 6.0 79.1 131.9 System Call Overhead 15000.0 246019.0 164.0 ======== System Benchmarks Index Score (Partial Only) 109.2 v6.8-rc6 + riscv/fixes + riscv/for-next + this patch series: System Benchmarks Partial Index BASELINE RESULT INDEX Execl Throughput 43.0 223.1 51.9 File Copy 1024 bufsize 2000 maxblocks 3960.0 71982.9 181.8 File Copy 256 bufsize 500 maxblocks 1655.0 18436.9 111.4 File Copy 4096 bufsize 8000 maxblocks 5800.0 184955.2 318.9 Pipe Throughput 12440.0 162622.9 130.7 Pipe-based Context Switching 4000.0 22082.5 55.2 Process Creation 126.0 546.4 43.4 Shell Scripts (1 concurrent) 42.4 598.1 141.1 Shell Scripts (16 concurrent) --- 38.8 --- Shell Scripts (8 concurrent) 6.0 78.6 131.0 System Call Overhead 15000.0 258529.3 172.4 ======== System Benchmarks Index Score (Partial Only) 112.8 [1]: https://lore.kernel.org/linux-riscv/20231030133027.19542-1-alexghiti@xxxxxxxxxxxx/ Changes in v5: - Rebase on v6.8-rc1 + riscv/for-next (for the fast GUP implementation) - Add patch for minor refactoring in asm/pgalloc.h - Also switch to riscv_use_sbi_for_rfence() in asm/pgalloc.h - Leave use_asid_allocator declared in asm/mmu_context.h Changes in v4: - Fix a possible race between flush_icache_*() and SMP bringup - Refactor riscv_use_ipi_for_rfence() to make later changes cleaner - Optimize kernel TLB flushes with only one CPU online - Optimize global cache/TLB flushes with only one CPU online - Merge the two copies of __flush_tlb_range() and rely on the compiler to optimize out the broadcast path (both clang and gcc do this) - Merge the two copies of flush_tlb_all() and rely on constant folding - Only set tlb_flush_all_threshold when CONFIG_MMU=y. Changes in v3: - Fixed a performance regression caused by executing sfence.vma in a loop on implementations affected by SiFive CIP-1200 - Rebased on v6.7-rc1 Changes in v2: - Move the SMP/UP merge earlier in the series to avoid build issues - Make a copy of __flush_tlb_range() instead of adding ifdefs inside - local_flush_tlb_all() is the only function used on !MMU (smpboot.c) Samuel Holland (13): riscv: Flush the instruction cache during SMP bringup riscv: Factor out page table TLB synchronization riscv: Use IPIs for remote cache/TLB flushes by default riscv: mm: Broadcast kernel TLB flushes only when needed riscv: Only send remote fences when some other CPU is online riscv: mm: Combine the SMP and UP TLB flush code riscv: Apply SiFive CIP-1200 workaround to single-ASID sfence.vma riscv: Avoid TLB flush loops when affected by SiFive CIP-1200 riscv: mm: Introduce cntx2asid/cntx2version helper macros riscv: mm: Use a fixed layout for the MM context ID riscv: mm: Make asid_bits a local variable riscv: mm: Preserve global TLB entries when switching contexts riscv: mm: Always use an ASID to flush mm contexts arch/riscv/Kconfig | 2 +- arch/riscv/errata/sifive/errata.c | 5 ++ arch/riscv/include/asm/errata_list.h | 12 ++++- arch/riscv/include/asm/mmu.h | 3 ++ arch/riscv/include/asm/pgalloc.h | 32 ++++++------ arch/riscv/include/asm/sbi.h | 4 ++ arch/riscv/include/asm/smp.h | 15 +----- arch/riscv/include/asm/tlbflush.h | 51 ++++++++----------- arch/riscv/kernel/sbi-ipi.c | 11 +++- arch/riscv/kernel/smp.c | 11 +--- arch/riscv/kernel/smpboot.c | 7 +-- arch/riscv/mm/Makefile | 5 +- arch/riscv/mm/cacheflush.c | 7 +-- arch/riscv/mm/context.c | 23 ++++----- arch/riscv/mm/tlbflush.c | 75 ++++++++-------------------- drivers/clocksource/timer-clint.c | 2 +- 16 files changed, 114 insertions(+), 151 deletions(-) -- 2.43.1
