On 21.06.22 22:46, Liam Howlett wrote: > From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> > > The maple tree was already tracking VMAs in this function by an earlier > commit, but the rbtree iterator was being used to iterate the list. > Change the iterator to use a maple tree native iterator and switch to the > maple tree advanced API to avoid multiple walks of the tree during insert > operations. Unexport the now-unused vma_store() function. > > For performance reasons we bulk allocate the maple tree nodes. The node > calculations are done internally to the tree and use the VMA count and > assume the worst-case node requirements. The VM_DONT_COPY flag does not > allow for the most efficient copy method of the tree and so a bulk loading > algorithm is used. You could track the #VM_DONT_COPY per mm and optimize? Do you have that planned or maybe it already is part of this patch set? :) > > Link: https://lkml.kernel.org/r/20220504010716.661115-16-Liam.Howlett@xxxxxxxxxx > Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: David Howells <dhowells@xxxxxxxxxx> > Cc: SeongJae Park <sj@xxxxxxxxxx> > Cc: Will Deacon <will@xxxxxxxxxx> > Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > include/linux/mm.h | 2 -- > kernel/fork.c | 12 +++++++++--- > 2 files changed, 9 insertions(+), 5 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f22c6f71a18c..27fa36a7c093 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2612,8 +2612,6 @@ extern bool arch_has_descending_max_zone_pfns(void); > /* nommu.c */ > extern atomic_long_t mmap_pages_allocated; > extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t); > -/* mmap.c */ > -void vma_mas_store(struct vm_area_struct *vma, struct ma_state *mas); > > /* interval_tree.c */ > void vma_interval_tree_insert(struct vm_area_struct *node, > diff --git a/kernel/fork.c b/kernel/fork.c > index 1840da0732f6..4ecca79556eb 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -583,9 +583,10 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, > struct vm_area_struct *mpnt, *tmp, *prev, **pprev; > struct rb_node **rb_link, *rb_parent; > int retval; > - unsigned long charge; > - LIST_HEAD(uf); > + unsigned long charge = 0; ^ why that change? > + MA_STATE(old_mas, &oldmm->mm_mt, 0, 0); > MA_STATE(mas, &mm->mm_mt, 0, 0); > + LIST_HEAD(uf); ^ why that reshuffling? > > uprobe_start_dup_mmap(); > if (mmap_write_lock_killable(oldmm)) { > @@ -620,7 +621,12 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, > goto out; > > prev = NULL; > - for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { > + > + retval = mas_expected_entries(&mas, oldmm->map_count); > + if (retval) > + goto out; mas_expected_entries is a fancy function :) > + > + mas_for_each(&old_mas, mpnt, ULONG_MAX) { > struct file *file; > > if (mpnt->vm_flags & VM_DONTCOPY) { -- Thanks, David / dhildenb
