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authorAlexandre Ghiti <alexghiti@rivosinc.com>2024-01-08 22:36:40 +0300
committerPalmer Dabbelt <palmer@rivosinc.com>2024-01-11 19:01:53 +0300
commit54d7431af73e2fa53b73cfeb2bec559c6664a4e4 (patch)
treec1a3c73c9d52a05cc6f6e4bf4bd411f44700218a /Documentation/features
parentff172d4818ad32dba433dae189e36684e43c5c74 (diff)
downloadlinux-54d7431af73e2fa53b73cfeb2bec559c6664a4e4.tar.xz
riscv: Add support for BATCHED_UNMAP_TLB_FLUSH
Allow to defer the flushing of the TLB when unmapping pages, which allows to reduce the numbers of IPI and the number of sfence.vma. The ubenchmarch used in commit 43b3dfdd0455 ("arm64: support batched/deferred tlb shootdown during page reclamation/migration") that was multithreaded to force the usage of IPI shows good performance improvement on all platforms: * Unmatched: ~34% * TH1520 : ~78% * Qemu : ~81% In addition, perf on qemu reports an important decrease in time spent dealing with IPIs: Before: 68.17% main [kernel.kallsyms] [k] __sbi_rfence_v02_call After : 8.64% main [kernel.kallsyms] [k] __sbi_rfence_v02_call * Benchmark: int stick_this_thread_to_core(int core_id) { int num_cores = sysconf(_SC_NPROCESSORS_ONLN); if (core_id < 0 || core_id >= num_cores) return EINVAL; cpu_set_t cpuset; CPU_ZERO(&cpuset); CPU_SET(core_id, &cpuset); pthread_t current_thread = pthread_self(); return pthread_setaffinity_np(current_thread, sizeof(cpu_set_t), &cpuset); } static void *fn_thread (void *p_data) { int ret; pthread_t thread; stick_this_thread_to_core((int)p_data); while (1) { sleep(1); } return NULL; } int main() { volatile unsigned char *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); pthread_t threads[4]; int ret; for (int i = 0; i < 4; ++i) { ret = pthread_create(&threads[i], NULL, fn_thread, (void *)i); if (ret) { printf("%s", strerror (ret)); } } memset(p, 0x88, SIZE); for (int k = 0; k < 10000; k++) { /* swap in */ for (int i = 0; i < SIZE; i += 4096) { (void)p[i]; } /* swap out */ madvise(p, SIZE, MADV_PAGEOUT); } for (int i = 0; i < 4; i++) { pthread_cancel(threads[i]); } for (int i = 0; i < 4; i++) { pthread_join(threads[i], NULL); } return 0; } Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> Reviewed-by: Jisheng Zhang <jszhang@kernel.org> Tested-by: Jisheng Zhang <jszhang@kernel.org> # Tested on TH1520 Tested-by: Nam Cao <namcao@linutronix.de> Link: https://lore.kernel.org/r/20240108193640.344929-1-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'Documentation/features')
-rw-r--r--Documentation/features/vm/TLB/arch-support.txt2
1 files changed, 1 insertions, 1 deletions
diff --git a/Documentation/features/vm/TLB/arch-support.txt b/Documentation/features/vm/TLB/arch-support.txt
index 8fd22073a847..d222bd3ee749 100644
--- a/Documentation/features/vm/TLB/arch-support.txt
+++ b/Documentation/features/vm/TLB/arch-support.txt
@@ -20,7 +20,7 @@
| openrisc: | .. |
| parisc: | TODO |
| powerpc: | TODO |
- | riscv: | TODO |
+ | riscv: | ok |
| s390: | TODO |
| sh: | TODO |
| sparc: | TODO |