On Tue, Feb 06, 2024 at 10:30:59PM -0500, rulinhuang wrote: > When allocating a new memory area where the mapping address range is > known, it is observed that the vmap_area lock is acquired twice. > The first acquisition occurs in the alloc_vmap_area() function when > inserting the vm area into the vm mapping red-black tree. The second > acquisition occurs in the setup_vmalloc_vm() function when updating the > properties of the vm, such as flags and address, etc. > Combine these two operations together in alloc_vmap_area(), which > improves scalability when the vmap_area lock is contended. By doing so, > the need to acquire the lock twice can also be eliminated. > With the above change, tested on intel icelake platform(160 vcpu, kernel > v6.7), a 6% performance improvement and a 7% reduction in overall > spinlock hotspot are gained on > stress-ng/pthread(https://github.com/ColinIanKing/stress-ng), which is > the stress test of thread creations. > > Reviewed-by: "Chen, Tim C" <tim.c.chen@xxxxxxxxx> > Reviewed-by: "King, Colin" <colin.king@xxxxxxxxx> > Signed-off-by: rulinhuang <rulin.huang@xxxxxxxxx> > --- > mm/vmalloc.c | 31 +++++++++++++++---------------- > 1 file changed, 15 insertions(+), 16 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d12a17fc0c171..3b1f616e8ecf0 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1577,13 +1577,13 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node) > > /* > * Allocate a region of KVA of the specified size and alignment, within the > - * vstart and vend. > + * vstart and vend. If vm is passed in, the two will also be bound. > */ > static struct vmap_area *alloc_vmap_area(unsigned long size, > unsigned long align, > unsigned long vstart, unsigned long vend, > int node, gfp_t gfp_mask, > - unsigned long va_flags) > + unsigned long va_flags, struct vm_struct *vm) > { > struct vmap_area *va; > unsigned long freed; > @@ -1627,9 +1627,12 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > > va->va_start = addr; > va->va_end = addr + size; > - va->vm = NULL; > + va->vm = vm; > va->flags = va_flags; > > + if (vm != NULL) > + vm->addr = (void *)addr; > + > spin_lock(&vmap_area_lock); > insert_vmap_area(va, &vmap_area_root, &vmap_area_list); > spin_unlock(&vmap_area_lock); > @@ -2039,7 +2042,8 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) > va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE, > VMALLOC_START, VMALLOC_END, > node, gfp_mask, > - VMAP_RAM|VMAP_BLOCK); > + VMAP_RAM|VMAP_BLOCK, > + NULL); > if (IS_ERR(va)) { > kfree(vb); > return ERR_CAST(va); > @@ -2394,7 +2398,8 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node) > struct vmap_area *va; > va = alloc_vmap_area(size, PAGE_SIZE, > VMALLOC_START, VMALLOC_END, > - node, GFP_KERNEL, VMAP_RAM); > + node, GFP_KERNEL, VMAP_RAM, > + NULL); > if (IS_ERR(va)) > return NULL; > > @@ -2548,14 +2553,6 @@ static inline void setup_vmalloc_vm_locked(struct vm_struct *vm, > va->vm = vm; > } > > -static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va, > - unsigned long flags, const void *caller) > -{ > - spin_lock(&vmap_area_lock); > - setup_vmalloc_vm_locked(vm, va, flags, caller); > - spin_unlock(&vmap_area_lock); > -} > - > static void clear_vm_uninitialized_flag(struct vm_struct *vm) > { > /* > @@ -2592,14 +2589,16 @@ static struct vm_struct *__get_vm_area_node(unsigned long size, > if (!(flags & VM_NO_GUARD)) > size += PAGE_SIZE; > > - va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0); > + area->flags = flags; > + area->caller = caller; > + area->size = size; > + > + va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area); > if (IS_ERR(va)) { > kfree(area); > return NULL; > } > > - setup_vmalloc_vm(area, va, flags, caller); > - > /* > Thank you for improving this! That was in my radar quite a long time ago :) Some comments though. I think that such "partial" way of initializing of "vm_struct" or "vm" is not optimal because it becomes spread between two places. Also, i think that we should not remove the setup_vmalloc_vm() function, instead we can move it in a place where the VA is not inserted to the tree, i.e. to initialize before insert. The "locked" variant can be renamed to setup_vmalloc_vm(). Also, could you please post how you tested this patch and stress-ng figures? This is really good for other people and folk to know. Thanks! -- Uladzislau Rezki
