On Tue, Mar 23, 2021 at 12:39:13PM +0000, Matthew Wilcox wrote:
> On Tue, Mar 23, 2021 at 01:04:36PM +0100, Uladzislau Rezki wrote:
> > On Mon, Mar 22, 2021 at 11:03:11PM +0000, Matthew Wilcox wrote:
> > > I suspect the vast majority of the time is spent calling alloc_pages_node()
> > > 1024 times. Have you looked at Mel's patch to do ... well, exactly what
> > > vmalloc() wants?
> > >
> > <snip>
> > - __vmalloc_node_range
> > - 45.25% __alloc_pages_nodemask
> > - 37.59% get_page_from_freelist
> [...]
> > - 44.61% 0xffffffffc047348d
> > - __vunmap
> > - 35.56% free_unref_page
>
> Hmm! I hadn't been thinking about the free side of things.
> Does this make a difference?
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4f5f8c907897..61d5b769fea0 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2277,16 +2277,8 @@ static void __vunmap(const void *addr, int deallocate_pages)
> vm_remove_mappings(area, deallocate_pages);
>
> if (deallocate_pages) {
> - int i;
> -
> - for (i = 0; i < area->nr_pages; i++) {
> - struct page *page = area->pages[i];
> -
> - BUG_ON(!page);
> - __free_pages(page, 0);
> - }
> + release_pages(area->pages, area->nr_pages);
> atomic_long_sub(area->nr_pages, &nr_vmalloc_pages);
> -
> kvfree(area->pages);
> }
>
Will check it today!
> release_pages does a bunch of checks that are unnecessary ... we could
> probably just do:
>
> LIST_HEAD(pages_to_free);
>
> for (i = 0; i < area->nr_pages; i++) {
> struct page *page = area->pages[i];
> if (put_page_testzero(page))
> list_add(&page->lru, &pages_to_free);
> }
> free_unref_page_list(&pages_to_free);
>
> but let's see if the provided interface gets us the performance we want.
>
> > Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> >
> > Thanks!
>
> Thank you!
You are welcome. A small nit:
CC mm/vmalloc.o
mm/vmalloc.c: In function ‘__vmalloc_area_node’:
mm/vmalloc.c:2492:14: warning: passing argument 4 of ‘kvmalloc_node_caller’ makes integer from pointer without a cast [-Wint-conversion]
area->caller);
~~~~^~~~~~~~
In file included from mm/vmalloc.c:12:
./include/linux/mm.h:782:7: note: expected ‘long unsigned int’ but argument is of type ‘const void *’
void *kvmalloc_node_caller(size_t size, gfp_t flags, int node,
<snip>
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8a202ba263f6..ee6fa44983bc 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2489,7 +2489,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
/* Please note that the recursion is strictly bounded. */
pages = kvmalloc_node_caller(array_size, nested_gfp, node,
- area->caller);
+ (unsigned long) area->caller);
if (!pages) {
free_vm_area(area);
return NULL;
<snip>
As for the bulk-array interface. I have checked the:
git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git mm-bulk-rebase-v6r2
applied the patch that is in question + below one:
<snip>
@@ -2503,25 +2498,13 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
area->pages = pages;
area->nr_pages = nr_pages;
- for (i = 0; i < area->nr_pages; i++) {
- struct page *page;
-
- if (node == NUMA_NO_NODE)
- page = alloc_page(gfp_mask);
- else
- page = alloc_pages_node(node, gfp_mask, 0);
-
- if (unlikely(!page)) {
- /* Successfully allocated i pages, free them in __vfree() */
- area->nr_pages = i;
- atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
- goto fail;
- }
- area->pages[i] = page;
- if (gfpflags_allow_blocking(gfp_mask))
- cond_resched();
+ ret = alloc_pages_bulk_array(gfp_mask, area->nr_pages, area->pages);
+ if (ret == nr_pages)
+ atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
+ else {
+ area->nr_pages = ret;
+ goto fail;
}
- atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
<snip>
single CPU, 4MB allocation, 1000000 avg: 70639437 usec
single CPU, 4MB allocation, 1000000 avg: 89218654 usec
and now we get ~21% delta. That is very good :)
--
Vlad Rezki
