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LoongArch: Try VMA lock-based page fault handling first 

Attempt VMA lock-based page fault handling first, and fall back to the
existing mmap_lock-based handling if that fails.

The "ebizzy -mTRp" test on Loongson-3A6000 shows that PER_VMA_LOCK can
improve the benchmark by about 17.9% (97837.7 to 115430.8).

This is the LoongArch variant of "x86/mm: try VMA lock-based page fault
handling first".

Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
pull/1354/merge
Wentao Guan 2025-10-02 22:39:19 +08:00 committed by Huacai Chen
parent c8168b4faf
commit 892979b0a9
2 changed files with 56 additions and 3 deletions
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1
arch/loongarch/Kconfig
View File

@ -69,6 +69,7 @@ config LOONGARCH
select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_LTO_CLANG_THIN
select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
select ARCH_SUPPORTS_NUMA_BALANCING select ARCH_SUPPORTS_NUMA_BALANCING
select ARCH_SUPPORTS_PER_VMA_LOCK
select ARCH_SUPPORTS_RT select ARCH_SUPPORTS_RT
select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF select ARCH_USE_CMPXCHG_LOCKREF

58
arch/loongarch/mm/fault.c
View File

@ -215,6 +215,58 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
flags |= FAULT_FLAG_USER; flags |= FAULT_FLAG_USER;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
if (!(flags & FAULT_FLAG_USER))
goto lock_mmap;
vma = lock_vma_under_rcu(mm, address);
if (!vma)
goto lock_mmap;
if (write) {
flags |= FAULT_FLAG_WRITE;
if (!(vma->vm_flags & VM_WRITE)) {
vma_end_read(vma);
si_code = SEGV_ACCERR;
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
goto bad_area_nosemaphore;
}
} else {
if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs)) {
vma_end_read(vma);
si_code = SEGV_ACCERR;
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
goto bad_area_nosemaphore;
}
if (!(vma->vm_flags & (VM_READ | VM_WRITE)) && address != exception_era(regs)) {
vma_end_read(vma);
si_code = SEGV_ACCERR;
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
goto bad_area_nosemaphore;
}
}
fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
vma_end_read(vma);
if (!(fault & VM_FAULT_RETRY)) {
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
goto done;
}
count_vm_vma_lock_event(VMA_LOCK_RETRY);
if (fault & VM_FAULT_MAJOR)
flags |= FAULT_FLAG_TRIED;
/* Quick path to respond to signals */
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
no_context(regs, write, address);
return;
}
lock_mmap:
retry: retry:
vma = lock_mm_and_find_vma(mm, address, regs); vma = lock_mm_and_find_vma(mm, address, regs);
if (unlikely(!vma)) if (unlikely(!vma))
@ -276,8 +328,10 @@ good_area:
*/ */
goto retry; goto retry;
} }
if (unlikely(fault & VM_FAULT_ERROR)) {
mmap_read_unlock(mm); mmap_read_unlock(mm);
done:
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM) { if (fault & VM_FAULT_OOM) {
do_out_of_memory(regs, write, address); do_out_of_memory(regs, write, address);
return; return;
@ -290,8 +344,6 @@ good_area:
} }
BUG(); BUG();
} }
mmap_read_unlock(mm);
} }
asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,