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Message-ID: <20210521130718.GA17882@pc638.lan>
Date: Fri, 21 May 2021 15:07:18 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
LKML <linux-kernel@...r.kernel.org>,
Mel Gorman <mgorman@...e.de>,
Christoph Hellwig <hch@...radead.org>,
Nicholas Piggin <npiggin@...il.com>,
Hillf Danton <hdanton@...a.com>,
Michal Hocko <mhocko@...e.com>,
Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] mm/vmalloc: Fallback to a single page allocator
On Fri, May 21, 2021 at 02:55:09PM +0200, Uladzislau Rezki wrote:
> > On Fri, May 21, 2021 at 01:10:33PM +0200, Uladzislau Rezki (Sony) wrote:
> > > +static inline unsigned int
> > > +vm_area_alloc_pages(gfp_t gfp, int nid, unsigned int page_order,
> > > + unsigned long nr_small_pages, struct page **pages)
> >
> > (at least) two tabs here, please, otherwise the argument list is at
> > the same indentation as the code which trips up my parser. some people
> > like to match the opening bracket, but that always feels like more work
> > than it's worth. fwiw, i'd format it like this:
> >
> > static inline unsigned int vm_area_alloc_pages(gfp_t gfp, int nid,
> > unsigned int order, unsigned long nr_pages, struct page **pages)
> > {
> > ...
> >
> No problem. Will fix it.
>
> >
> > (yes, i renamed some of the variables there; overly long variable names
> > are painful)
> >
> > The rest of the patch looks good.
> >
> > Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Thank you!
>
> I will re-spin the patch and send a v2.
>
>From 6537bc97b5550f17b0813caf02ce0ec1865fa94e Mon Sep 17 00:00:00 2001
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
Date: Thu, 20 May 2021 14:13:23 +0200
Subject: [PATCH v2] mm/vmalloc: Fallback to a single page allocator
Currently for order-0 pages we use a bulk-page allocator to get
set of pages. From the other hand not allocating all pages is
something that might occur. In that case we should fallbak to
the single-page allocator trying to get missing pages, because
it is more permissive(direct reclaim, etc).
Introduce a vm_area_alloc_pages() function where the described
logic is implemented.
Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
mm/vmalloc.c | 81 +++++++++++++++++++++++++++++++++-------------------
1 file changed, 52 insertions(+), 29 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b2a0cbfa37c1..7765af7b1e9c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2756,6 +2756,54 @@ void *vmap_pfn(unsigned long *pfns, unsigned int count, pgprot_t prot)
EXPORT_SYMBOL_GPL(vmap_pfn);
#endif /* CONFIG_VMAP_PFN */
+static inline unsigned int
+vm_area_alloc_pages(gfp_t gfp, int nid,
+ unsigned int order, unsigned long nr_pages, struct page **pages)
+{
+ unsigned int nr_allocated = 0;
+
+ /*
+ * For order-0 pages we make use of bulk allocator, if
+ * the page array is partly or not at all populated due
+ * to fails, fallback to a single page allocator that is
+ * more permissive.
+ */
+ if (!order)
+ nr_allocated = alloc_pages_bulk_array_node(
+ gfp, nid, nr_pages, pages);
+ else
+ /*
+ * Compound pages required for remap_vmalloc_page if
+ * high-order pages.
+ */
+ gfp |= __GFP_COMP;
+
+ /* High-order pages or fallback path if "bulk" fails. */
+ while (nr_allocated < nr_pages) {
+ struct page *page;
+ int i;
+
+ page = alloc_pages_node(nid, gfp, order);
+ if (unlikely(!page))
+ break;
+
+ /*
+ * Careful, we allocate and map page-order pages, but
+ * tracking is done per PAGE_SIZE page so as to keep the
+ * vm_struct APIs independent of the physical/mapped size.
+ */
+ for (i = 0; i < (1U << order); i++)
+ pages[nr_allocated + i] = page + i;
+
+ if (gfpflags_allow_blocking(gfp))
+ cond_resched();
+
+ nr_allocated += 1U << order;
+ }
+
+ return nr_allocated;
+}
+
static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
pgprot_t prot, unsigned int page_shift,
int node)
@@ -2789,37 +2837,11 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
return NULL;
}
- area->nr_pages = 0;
set_vm_area_page_order(area, page_shift - PAGE_SHIFT);
page_order = vm_area_page_order(area);
- if (!page_order) {
- area->nr_pages = alloc_pages_bulk_array_node(
- gfp_mask, node, nr_small_pages, area->pages);
- } else {
- /*
- * Careful, we allocate and map page_order pages, but tracking is done
- * per PAGE_SIZE page so as to keep the vm_struct APIs independent of
- * the physical/mapped size.
- */
- while (area->nr_pages < nr_small_pages) {
- struct page *page;
- int i;
-
- /* Compound pages required for remap_vmalloc_page */
- page = alloc_pages_node(node, gfp_mask | __GFP_COMP, page_order);
- if (unlikely(!page))
- break;
-
- for (i = 0; i < (1U << page_order); i++)
- area->pages[area->nr_pages + i] = page + i;
-
- if (gfpflags_allow_blocking(gfp_mask))
- cond_resched();
-
- area->nr_pages += 1U << page_order;
- }
- }
+ area->nr_pages = vm_area_alloc_pages(gfp_mask, node,
+ page_order, nr_small_pages, area->pages);
atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
@@ -2835,7 +2857,8 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
goto fail;
}
- if (vmap_pages_range(addr, addr + size, prot, area->pages, page_shift) < 0) {
+ if (vmap_pages_range(addr, addr + size, prot, area->pages,
+ page_shift) < 0) {
warn_alloc(gfp_mask, NULL,
"vmalloc size %lu allocation failure: "
"failed to map pages",
--
2.20.1
--
Vlad Rezki
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