On Tue, Dec 20, 2022 at 07:45:20PM +0100, Uladzislau Rezki wrote:
> On Tue, Dec 20, 2022 at 07:27:03PM +0100, Uladzislau Rezki (Sony) wrote:
> > When a VA is freed over a main path, for example by invoking
> > the vfree() function, a tree is accessed two times what is odd:
> >
> > vfree():
> > __vunmap()
> > __find_vmap_area()
> > vm_remove_mappings()
> > remove_vm_area()
> > __find_vmap_area()
> >
> > __find_vmap_area() are called two times. Fix it by introducing
> > a find_unlink_vmap_area() helper that finds and un-links a VA
> > from a tree.
> >
> > Performance test results on a single CPU:
> >
> > - fix_size_alloc_test loops: 1000000 avg: 476847 usec
> > - full_fit_alloc_test loops: 1000000 avg: 806746 usec
> > - long_busy_list_alloc_test loops: 1000000 avg: 13552093 usec
> > - random_size_alloc_test loops: 1000000 avg: 7441322 usec
> > - fix_align_alloc_test loops: 1000000 avg: 1411132 usec
> > All test took worker0=87650866284 cycles
> >
> > - fix_size_alloc_test loops: 1000000 avg: 490713 usec
> > - full_fit_alloc_test loops: 1000000 avg: 579162 usec
> > - long_busy_list_alloc_test loops: 1000000 avg: 10485448 usec
> > - random_size_alloc_test loops: 1000000 avg: 5824449 usec
> > - fix_align_alloc_test loops: 1000000 avg: 984735 usec
> > All test took worker0=67952362802 cycles
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> > ---
> > mm/vmalloc.c | 40 ++++++++++++++++++++++++++++------------
> > 1 file changed, 28 insertions(+), 12 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 9e30f0b39203..0fc38c36e0df 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -1825,9 +1825,14 @@ static void free_vmap_area_noflush(struct vmap_area *va)
> > unsigned long va_start = va->va_start;
> > unsigned long nr_lazy;
> >
> > - spin_lock(&vmap_area_lock);
> > - unlink_va(va, &vmap_area_root);
> > - spin_unlock(&vmap_area_lock);
> > + /*
> > + * A free_vmap_block() is left. It is NOT a main free path.
> > + */
> > + if (!list_empty(&va->list)) {
> > + spin_lock(&vmap_area_lock);
> > + unlink_va(va, &vmap_area_root);
> > + spin_unlock(&vmap_area_lock);
> > + }
> >
> > nr_lazy = atomic_long_add_return((va->va_end - va->va_start) >>
> > PAGE_SHIFT, &vmap_lazy_nr);
> > @@ -1871,6 +1876,19 @@ struct vmap_area *find_vmap_area(unsigned long addr)
> > return va;
> > }
> >
> > +static struct vmap_area *find_unlink_vmap_area(unsigned long addr)
> > +{
> > + struct vmap_area *va;
> > +
> > + spin_lock(&vmap_area_lock);
> > + va = __find_vmap_area(addr, &vmap_area_root);
> > + if (va)
> > + unlink_va(va, &vmap_area_root);
> > + spin_unlock(&vmap_area_lock);
> > +
> > + return va;
> > +}
> > +
> > /*** Per cpu kva allocator ***/
> >
> > /*
> > @@ -2236,7 +2254,7 @@ void vm_unmap_ram(const void *mem, unsigned int count)
> > return;
> > }
> >
> > - va = find_vmap_area(addr);
> > + va = find_unlink_vmap_area(addr);
> > BUG_ON(!va);
> > debug_check_no_locks_freed((void *)va->va_start,
> > (va->va_end - va->va_start));
> > @@ -2607,21 +2625,16 @@ struct vm_struct *remove_vm_area(const void *addr)
> >
> > might_sleep();
> >
> > - spin_lock(&vmap_area_lock);
> > - va = __find_vmap_area((unsigned long)addr, &vmap_area_root);
> > - if (va && va->vm) {
> > + va = find_unlink_vmap_area((unsigned long) addr);
> > + if (va) {
> > struct vm_struct *vm = va->vm;
> >
> > - va->vm = NULL;
> > - spin_unlock(&vmap_area_lock);
> > -
> > kasan_free_module_shadow(vm);
> > free_unmap_vmap_area(va);
> >
> > return vm;
> > }
> >
> > - spin_unlock(&vmap_area_lock);
> > return NULL;
> > }
> >
> > @@ -2690,6 +2703,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
> > static void __vunmap(const void *addr, int deallocate_pages)
> > {
> > struct vm_struct *area;
> > + struct vmap_area *va;
> >
> > if (!addr)
> > return;
> > @@ -2698,7 +2712,9 @@ static void __vunmap(const void *addr, int deallocate_pages)
> > addr))
> > return;
> >
> > - area = find_vm_area(addr);
> > + va = find_unlink_vmap_area((unsigned long)addr);
> > + area = va->vm;
> > +
> > if (unlikely(!area)) {
> > WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n",
> > addr);
> > --
> > 2.30.2
> >
Will send a v2.
--
Uladzislau Rezki
