From: Mateusz Guzik Date: Tue, 21 May 2024 23:43:21 +0000 (+0200) Subject: mm: batch unlink_file_vma calls in free_pgd_range X-Git-Tag: microblaze-v6.13~589^2~368 X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=3577dbb192419e37b6f54aced8777b6c81cd03d4;p=linux-2.6-microblaze.git mm: batch unlink_file_vma calls in free_pgd_range Execs of dynamically linked binaries at 20-ish cores are bottlenecked on the i_mmap_rwsem semaphore, while the biggest singular contributor is free_pgd_range inducing the lock acquire back-to-back for all consecutive mappings of a given file. Tracing the count of said acquires while building the kernel shows: [1, 2) 799579 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [2, 3) 0 | | [3, 4) 3009 | | [4, 5) 3009 | | [5, 6) 326442 |@@@@@@@@@@@@@@@@@@@@@ | So in particular there were 326442 opportunities to coalesce 5 acquires into 1. Doing so increases execs per second by 4% (~50k to ~52k) when running the benchmark linked below. The lock remains the main bottleneck, I have not looked at other spots yet. Bench can be found here: http://apollo.backplane.com/DFlyMisc/doexec.c $ cc -O2 -o shared-doexec doexec.c $ ./shared-doexec $(nproc) Note this particular test makes sure binaries are separate, but the loader is shared. Stats collected on the patched kernel (+ "noinline") with: bpftrace -e 'kprobe:unlink_file_vma_batch_process { @ = lhist(((struct unlink_vma_file_batch *)arg0)->count, 0, 8, 1); }' Link: https://lkml.kernel.org/r/20240521234321.359501-1-mjguzik@gmail.com Signed-off-by: Mateusz Guzik Reviewed-by: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- diff --git a/mm/internal.h b/mm/internal.h index 6902b7dd8509..774bf23b030c 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1515,4 +1515,13 @@ static inline void shrinker_debugfs_remove(struct dentry *debugfs_entry, void workingset_update_node(struct xa_node *node); extern struct list_lru shadow_nodes; +struct unlink_vma_file_batch { + int count; + struct vm_area_struct *vmas[8]; +}; + +void unlink_file_vma_batch_init(struct unlink_vma_file_batch *); +void unlink_file_vma_batch_add(struct unlink_vma_file_batch *, struct vm_area_struct *); +void unlink_file_vma_batch_final(struct unlink_vma_file_batch *); + #endif /* __MM_INTERNAL_H */ diff --git a/mm/memory.c b/mm/memory.c index edf2004fcdf9..1411edbb55d0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -365,6 +365,8 @@ void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas, struct vm_area_struct *vma, unsigned long floor, unsigned long ceiling, bool mm_wr_locked) { + struct unlink_vma_file_batch vb; + do { unsigned long addr = vma->vm_start; struct vm_area_struct *next; @@ -384,12 +386,15 @@ void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas, if (mm_wr_locked) vma_start_write(vma); unlink_anon_vmas(vma); - unlink_file_vma(vma); if (is_vm_hugetlb_page(vma)) { + unlink_file_vma(vma); hugetlb_free_pgd_range(tlb, addr, vma->vm_end, floor, next ? next->vm_start : ceiling); } else { + unlink_file_vma_batch_init(&vb); + unlink_file_vma_batch_add(&vb, vma); + /* * Optimization: gather nearby vmas into one call down */ @@ -402,8 +407,9 @@ void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas, if (mm_wr_locked) vma_start_write(vma); unlink_anon_vmas(vma); - unlink_file_vma(vma); + unlink_file_vma_batch_add(&vb, vma); } + unlink_file_vma_batch_final(&vb); free_pgd_range(tlb, addr, vma->vm_end, floor, next ? next->vm_start : ceiling); } diff --git a/mm/mmap.c b/mm/mmap.c index 83b4682ec85c..e42d89f98071 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -131,6 +131,47 @@ void unlink_file_vma(struct vm_area_struct *vma) } } +void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb) +{ + vb->count = 0; +} + +static void unlink_file_vma_batch_process(struct unlink_vma_file_batch *vb) +{ + struct address_space *mapping; + int i; + + mapping = vb->vmas[0]->vm_file->f_mapping; + i_mmap_lock_write(mapping); + for (i = 0; i < vb->count; i++) { + VM_WARN_ON_ONCE(vb->vmas[i]->vm_file->f_mapping != mapping); + __remove_shared_vm_struct(vb->vmas[i], mapping); + } + i_mmap_unlock_write(mapping); + + unlink_file_vma_batch_init(vb); +} + +void unlink_file_vma_batch_add(struct unlink_vma_file_batch *vb, + struct vm_area_struct *vma) +{ + if (vma->vm_file == NULL) + return; + + if ((vb->count > 0 && vb->vmas[0]->vm_file != vma->vm_file) || + vb->count == ARRAY_SIZE(vb->vmas)) + unlink_file_vma_batch_process(vb); + + vb->vmas[vb->count] = vma; + vb->count++; +} + +void unlink_file_vma_batch_final(struct unlink_vma_file_batch *vb) +{ + if (vb->count > 0) + unlink_file_vma_batch_process(vb); +} + /* * Close a vm structure and free it. */