[PATCH v3 net-next 0/5] net: consolidate page_is_pfmemalloc() usage

[PATCH v3 net-next 0/5] net: consolidate page_is_pfmemalloc() usage

[Alexander Lobakin]

page_is_pfmemalloc() is used mostly by networking drivers to test
if a page can be considered for reusing/recycling.
It doesn't write anything to the struct page itself, so its sole
argument can be constified, as well as the first argument of
skb_propagate_pfmemalloc().
In Page Pool core code, it can be simply inlined instead.
Most of the callers from NIC drivers were just doppelgangers of
the same condition tests. Derive them into a new common function
do deduplicate the code.

Since v2 [1]:
 - use more intuitive name for the new inline function since there's
   nothing "reserved" in remote pages (Jakub Kicinski, John Hubbard);
 - fold likely() inside the helper itself to make driver code a bit
   fancier (Jakub Kicinski);
 - split function introduction and using into two separate commits;
 - collect some more tags (Jesse Brandeburg, David Rientjes).

Since v1 [0]:
 - new: reduce code duplication by introducing a new common function
   to test if a page can be reused/recycled (David Rientjes);
 - collect autographs for Page Pool bits (Jesper Dangaard Brouer,
   Ilias Apalodimas).

[0] https://lore.kernel.org/netdev/20210125164612.243838-1-alobakin@pm.me
[1] https://lore.kernel.org/netdev/20210127201031.98544-1-alobakin@pm.me

Alexander Lobakin (5):
  mm: constify page_is_pfmemalloc() argument
  skbuff: constify skb_propagate_pfmemalloc() "page" argument
  net: introduce common dev_page_is_reusable()
  net: use the new dev_page_is_reusable() instead of private versions
  net: page_pool: simplify page recycling condition tests

 .../net/ethernet/hisilicon/hns3/hns3_enet.c   | 17 ++++++----------
 drivers/net/ethernet/intel/fm10k/fm10k_main.c | 13 ++++--------
 drivers/net/ethernet/intel/i40e/i40e_txrx.c   | 15 +-------------
 drivers/net/ethernet/intel/iavf/iavf_txrx.c   | 15 +-------------
 drivers/net/ethernet/intel/ice/ice_txrx.c     | 13 ++----------
 drivers/net/ethernet/intel/igb/igb_main.c     |  9 ++-------
 drivers/net/ethernet/intel/igc/igc_main.c     |  9 ++-------
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |  9 ++-------
 .../net/ethernet/intel/ixgbevf/ixgbevf_main.c |  9 ++-------
 .../net/ethernet/mellanox/mlx5/core/en_rx.c   |  7 +------
 include/linux/mm.h                            |  2 +-
 include/linux/skbuff.h                        | 20 +++++++++++++++++--
 net/core/page_pool.c                          | 14 ++++---------
 13 files changed, 46 insertions(+), 106 deletions(-)

-- 
2.30.0

[PATCH v3 net-next 1/5] mm: constify page_is_pfmemalloc() argument

[Alexander Lobakin]

The function only tests for page->index, so its argument should be
const.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
---
 include/linux/mm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ecdf8a8cd6ae..078633d43af9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1584,7 +1584,7 @@ struct address_space *page_mapping_file(struct page *page);
  * ALLOC_NO_WATERMARKS and the low watermark was not
  * met implying that the system is under some pressure.
  */
-static inline bool page_is_pfmemalloc(struct page *page)
+static inline bool page_is_pfmemalloc(const struct page *page)
 {
 	/*
 	 * Page index cannot be this large so this must be
-- 
2.30.0

[PATCH v3 net-next 3/5] net: introduce common dev_page_is_reusable()

[Alexander Lobakin]

A bunch of drivers test the page before reusing/recycling for two
common conditions:
 - if a page was allocated under memory pressure (pfmemalloc page);
 - if a page was allocated at a distant memory node (to exclude
   slowdowns).

Introduce a new common inline for doing this, with likely() already
folded inside to make driver code a bit simpler.

Suggested-by: David Rientjes <rientjes@google.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
---
 include/linux/skbuff.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b027526da4f9..0e42c53b8ca9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2938,6 +2938,22 @@ static inline struct page *dev_alloc_page(void)
 	return dev_alloc_pages(0);
 }
 
+/**
+ * dev_page_is_reusable - check whether a page can be reused for network Rx
+ * @page: the page to test
+ *
+ * A page shouldn't be considered for reusing/recycling if it was allocated
+ * under memory pressure or at a distant memory node.
+ *
+ * Returns false if this page should be returned to page allocator, true
+ * otherwise.
+ */
+static inline bool dev_page_is_reusable(const struct page *page)
+{
+	return likely(page_to_nid(page) == numa_mem_id() &&
+		      !page_is_pfmemalloc(page));
+}
+
 /**
  *	skb_propagate_pfmemalloc - Propagate pfmemalloc if skb is allocated after RX page
  *	@page: The page that was allocated from skb_alloc_page
-- 
2.30.0

Re: [PATCH v3 net-next 3/5] net: introduce common dev_page_is_reusable()

[Alexander Lobakin]

From: Matthew Wilcox <willy@infradead.org>
Date: Sun, 31 Jan 2021 12:22:05 +0000

> On Sun, Jan 31, 2021 at 12:11:52PM +0000, Alexander Lobakin wrote:
> > A bunch of drivers test the page before reusing/recycling for two
> > common conditions:
> >  - if a page was allocated under memory pressure (pfmemalloc page);
> >  - if a page was allocated at a distant memory node (to exclude
> >    slowdowns).
> >
> > Introduce a new common inline for doing this, with likely() already
> > folded inside to make driver code a bit simpler.
> 
> I don't see the need for the 'dev_' prefix.  That actually confuses me
> because it makes me think this is tied to ZONE_DEVICE or some such.

Several functions right above this one also use 'dev_' prefix. It's
a rather old mark that it's about network devices.

> So how about calling it just 'page_is_reusable' and putting it in mm.h
> with page_is_pfmemalloc() and making the comment a little less network-centric?

This pair of conditions (!pfmemalloc + local memory node) is really
specific to network drivers. I didn't see any other instances of such
tests, so I don't see a reason to place it in a more common mm.h.

> Or call it something like skb_page_is_recyclable() since it's only used
> by networking today.  But I bet it could/should be used more widely.

There's nothing about skb. Tested page is just a memory chunk for DMA
transaction. It can be used as skb head/frag, for XDP buffer/frame or
for XSK umem.

> > +/**
> > + * dev_page_is_reusable - check whether a page can be reused for network Rx
> > + * @page: the page to test
> > + *
> > + * A page shouldn't be considered for reusing/recycling if it was allocated
> > + * under memory pressure or at a distant memory node.
> > + *
> > + * Returns false if this page should be returned to page allocator, true
> > + * otherwise.
> > + */
> > +static inline bool dev_page_is_reusable(const struct page *page)
> > +{
> > +	return likely(page_to_nid(page) == numa_mem_id() &&
> > +		      !page_is_pfmemalloc(page));
> > +}
> > +

Al

Re: [PATCH v3 net-next 0/5] net: consolidate page_is_pfmemalloc() usage

[Jakub Kicinski]

On Sun, 31 Jan 2021 12:11:16 +0000 Alexander Lobakin wrote:
> page_is_pfmemalloc() is used mostly by networking drivers to test
> if a page can be considered for reusing/recycling.
> It doesn't write anything to the struct page itself, so its sole
> argument can be constified, as well as the first argument of
> skb_propagate_pfmemalloc().
> In Page Pool core code, it can be simply inlined instead.
> Most of the callers from NIC drivers were just doppelgangers of
> the same condition tests. Derive them into a new common function
> do deduplicate the code.

Please resend, this did not get into patchwork :/

Re: [PATCH v3 net-next 0/5] net: consolidate page_is_pfmemalloc() usage

[Alexander Lobakin]

From: Jakub Kicinski <kuba@kernel.org>
Date: Mon, 1 Feb 2021 17:18:35 -0800

> On Sun, 31 Jan 2021 12:11:16 +0000 Alexander Lobakin wrote:
> > page_is_pfmemalloc() is used mostly by networking drivers to test
> > if a page can be considered for reusing/recycling.
> > It doesn't write anything to the struct page itself, so its sole
> > argument can be constified, as well as the first argument of
> > skb_propagate_pfmemalloc().
> > In Page Pool core code, it can be simply inlined instead.
> > Most of the callers from NIC drivers were just doppelgangers of
> > the same condition tests. Derive them into a new common function
> > do deduplicate the code.
> 
> Please resend, this did not get into patchwork :/

I suspected it would be so as I got reports about undelivered mails
due to unavailability of vger.kernel.org for some reasons Will do.

Al