[PATCH net-next v16 05/13] page_pool: devmem support
From: Mina Almasry
Date: Tue Jul 09 2024 - 20:22:49 EST
Convert netmem to be a union of struct page and struct netmem. Overload
the LSB of struct netmem* to indicate that it's a net_iov, otherwise
it's a page.
Currently these entries in struct page are rented by the page_pool and
used exclusively by the net stack:
struct {
unsigned long pp_magic;
struct page_pool *pp;
unsigned long _pp_mapping_pad;
unsigned long dma_addr;
atomic_long_t pp_ref_count;
};
Mirror these (and only these) entries into struct net_iov and implement
netmem helpers that can access these common fields regardless of
whether the underlying type is page or net_iov.
Implement checks for net_iov in netmem helpers which delegate to mm
APIs, to ensure net_iov are never passed to the mm stack.
Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Reviewed-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
v13:
- Move NET_IOV dependent changes to this patch.
- Fixed comment (Pavel)
- Applied Reviewed-by from Pavel.
v9: https://lore.kernel.org/netdev/20240403002053.2376017-8-almasrymina@xxxxxxxxxx/
- Remove CONFIG checks in netmem_is_net_iov() (Pavel/David/Jens)
v7:
- Remove static_branch_unlikely from netmem_to_net_iov(). We're getting
better results from the fast path in bench_page_pool_simple tests
without the static_branch_unlikely, and the addition of
static_branch_unlikely doesn't improve performance of devmem TCP.
Additionally only check netmem_to_net_iov() if
CONFIG_DMA_SHARED_BUFFER is enabled, otherwise dmabuf net_iovs cannot
exist anyway.
net-next base: 8 cycle fast path.
with static_branch_unlikely: 10 cycle fast path.
without static_branch_unlikely: 9 cycle fast path.
CONFIG_DMA_SHARED_BUFFER disabled: 8 cycle fast path as baseline.
Performance of devmem TCP is at 95% line rate is regardless of
static_branch_unlikely or not.
v6:
- Rebased on top of the merged netmem_ref type.
- Rebased on top of the merged skb_pp_frag_ref() changes.
v5:
- Use netmem instead of page* with LSB set.
- Use pp_ref_count for refcounting net_iov.
- Removed many of the custom checks for netmem.
v1:
- Disable fragmentation support for iov properly.
- fix napi_pp_put_page() path (Yunsheng).
- Use pp_frag_count for devmem refcounting.
Cc: linux-mm@xxxxxxxxx
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
---
include/net/netmem.h | 137 +++++++++++++++++++++++++++++--
include/net/page_pool/helpers.h | 25 +++---
include/trace/events/page_pool.h | 8 +-
net/core/devmem.c | 3 +
net/core/page_pool.c | 24 +++---
net/core/skbuff.c | 22 +++--
6 files changed, 171 insertions(+), 48 deletions(-)
diff --git a/include/net/netmem.h b/include/net/netmem.h
index 664df8325ece5..35ad237fdf29e 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -9,14 +9,51 @@
#define _NET_NETMEM_H
#include <net/devmem.h>
+#include <net/net_debug.h>
/* net_iov */
+DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
+
+/* We overload the LSB of the struct page pointer to indicate whether it's
+ * a page or net_iov.
+ */
+#define NET_IOV 0x01UL
+
struct net_iov {
+ unsigned long __unused_padding;
+ unsigned long pp_magic;
+ struct page_pool *pp;
struct dmabuf_genpool_chunk_owner *owner;
unsigned long dma_addr;
+ atomic_long_t pp_ref_count;
};
+/* These fields in struct page are used by the page_pool and net stack:
+ *
+ * struct {
+ * unsigned long pp_magic;
+ * struct page_pool *pp;
+ * unsigned long _pp_mapping_pad;
+ * unsigned long dma_addr;
+ * atomic_long_t pp_ref_count;
+ * };
+ *
+ * We mirror the page_pool fields here so the page_pool can access these fields
+ * without worrying whether the underlying fields belong to a page or net_iov.
+ *
+ * The non-net stack fields of struct page are private to the mm stack and must
+ * never be mirrored to net_iov.
+ */
+#define NET_IOV_ASSERT_OFFSET(pg, iov) \
+ static_assert(offsetof(struct page, pg) == \
+ offsetof(struct net_iov, iov))
+NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic);
+NET_IOV_ASSERT_OFFSET(pp, pp);
+NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr);
+NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
+#undef NET_IOV_ASSERT_OFFSET
+
static inline struct dmabuf_genpool_chunk_owner *
net_iov_owner(const struct net_iov *niov)
{
@@ -47,20 +84,22 @@ net_iov_binding(const struct net_iov *niov)
*/
typedef unsigned long __bitwise netmem_ref;
+static inline bool netmem_is_net_iov(const netmem_ref netmem)
+{
+ return (__force unsigned long)netmem & NET_IOV;
+}
+
/* This conversion fails (returns NULL) if the netmem_ref is not struct page
* backed.
- *
- * Currently struct page is the only possible netmem, and this helper never
- * fails.
*/
static inline struct page *netmem_to_page(netmem_ref netmem)
{
+ if (WARN_ON_ONCE(netmem_is_net_iov(netmem)))
+ return NULL;
+
return (__force struct page *)netmem;
}
-/* Converting from page to netmem is always safe, because a page can always be
- * a netmem.
- */
static inline netmem_ref page_to_netmem(struct page *page)
{
return (__force netmem_ref)page;
@@ -68,17 +107,103 @@ static inline netmem_ref page_to_netmem(struct page *page)
static inline int netmem_ref_count(netmem_ref netmem)
{
+ /* The non-pp refcount of net_iov is always 1. On net_iov, we only
+ * support pp refcounting which uses the pp_ref_count field.
+ */
+ if (netmem_is_net_iov(netmem))
+ return 1;
+
return page_ref_count(netmem_to_page(netmem));
}
static inline unsigned long netmem_to_pfn(netmem_ref netmem)
{
+ if (netmem_is_net_iov(netmem))
+ return 0;
+
return page_to_pfn(netmem_to_page(netmem));
}
+static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem)
+{
+ return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV);
+}
+
+static inline unsigned long netmem_get_pp_magic(netmem_ref netmem)
+{
+ return __netmem_clear_lsb(netmem)->pp_magic;
+}
+
+static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned long pp_magic)
+{
+ __netmem_clear_lsb(netmem)->pp_magic |= pp_magic;
+}
+
+static inline void netmem_clear_pp_magic(netmem_ref netmem)
+{
+ __netmem_clear_lsb(netmem)->pp_magic = 0;
+}
+
+static inline struct page_pool *netmem_get_pp(netmem_ref netmem)
+{
+ return __netmem_clear_lsb(netmem)->pp;
+}
+
+static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *pool)
+{
+ __netmem_clear_lsb(netmem)->pp = pool;
+}
+
+static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
+{
+ return __netmem_clear_lsb(netmem)->dma_addr;
+}
+
+static inline void netmem_set_dma_addr(netmem_ref netmem,
+ unsigned long dma_addr)
+{
+ __netmem_clear_lsb(netmem)->dma_addr = dma_addr;
+}
+
+static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem)
+{
+ return &__netmem_clear_lsb(netmem)->pp_ref_count;
+}
+
+static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid)
+{
+ /* Assume net_iov are on the preferred node without actually
+ * checking...
+ *
+ * This check is only used to check for recycling memory in the page
+ * pool's fast paths. Currently the only implementation of net_iov
+ * is dmabuf device memory. It's a deliberate decision by the user to
+ * bind a certain dmabuf to a certain netdev, and the netdev rx queue
+ * would not be able to reallocate memory from another dmabuf that
+ * exists on the preferred node, so, this check doesn't make much sense
+ * in this case. Assume all net_iovs can be recycled for now.
+ */
+ if (netmem_is_net_iov(netmem))
+ return true;
+
+ return page_to_nid(netmem_to_page(netmem)) == pref_nid;
+}
+
static inline netmem_ref netmem_compound_head(netmem_ref netmem)
{
+ /* niov are never compounded */
+ if (netmem_is_net_iov(netmem))
+ return netmem;
+
return page_to_netmem(compound_head(netmem_to_page(netmem)));
}
+static inline void *netmem_address(netmem_ref netmem)
+{
+ if (netmem_is_net_iov(netmem))
+ return NULL;
+
+ return page_address(netmem_to_page(netmem));
+}
+
#endif /* _NET_NETMEM_H */
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 2b43a893c619d..0c95594ce8e1c 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -216,7 +216,7 @@ page_pool_get_dma_dir(const struct page_pool *pool)
static inline void page_pool_fragment_netmem(netmem_ref netmem, long nr)
{
- atomic_long_set(&netmem_to_page(netmem)->pp_ref_count, nr);
+ atomic_long_set(netmem_get_pp_ref_count_ref(netmem), nr);
}
/**
@@ -244,7 +244,7 @@ static inline void page_pool_fragment_page(struct page *page, long nr)
static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
{
- struct page *page = netmem_to_page(netmem);
+ atomic_long_t *pp_ref_count = netmem_get_pp_ref_count_ref(netmem);
long ret;
/* If nr == pp_ref_count then we have cleared all remaining
@@ -261,19 +261,19 @@ static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
* initially, and only overwrite it when the page is partitioned into
* more than one piece.
*/
- if (atomic_long_read(&page->pp_ref_count) == nr) {
+ if (atomic_long_read(pp_ref_count) == nr) {
/* As we have ensured nr is always one for constant case using
* the BUILD_BUG_ON(), only need to handle the non-constant case
* here for pp_ref_count draining, which is a rare case.
*/
BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
if (!__builtin_constant_p(nr))
- atomic_long_set(&page->pp_ref_count, 1);
+ atomic_long_set(pp_ref_count, 1);
return 0;
}
- ret = atomic_long_sub_return(nr, &page->pp_ref_count);
+ ret = atomic_long_sub_return(nr, pp_ref_count);
WARN_ON(ret < 0);
/* We are the last user here too, reset pp_ref_count back to 1 to
@@ -282,7 +282,7 @@ static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
* page_pool_unref_page() currently.
*/
if (unlikely(!ret))
- atomic_long_set(&page->pp_ref_count, 1);
+ atomic_long_set(pp_ref_count, 1);
return ret;
}
@@ -401,9 +401,7 @@ static inline void page_pool_free_va(struct page_pool *pool, void *va,
static inline dma_addr_t page_pool_get_dma_addr_netmem(netmem_ref netmem)
{
- struct page *page = netmem_to_page(netmem);
-
- dma_addr_t ret = page->dma_addr;
+ dma_addr_t ret = netmem_get_dma_addr(netmem);
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
ret <<= PAGE_SHIFT;
@@ -426,18 +424,17 @@ static inline dma_addr_t page_pool_get_dma_addr(const struct page *page)
static inline bool page_pool_set_dma_addr_netmem(netmem_ref netmem,
dma_addr_t addr)
{
- struct page *page = netmem_to_page(netmem);
-
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
- page->dma_addr = addr >> PAGE_SHIFT;
+ netmem_set_dma_addr(netmem, addr >> PAGE_SHIFT);
/* We assume page alignment to shave off bottom bits,
* if this "compression" doesn't work we need to drop.
*/
- return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
+ return addr != (dma_addr_t)netmem_get_dma_addr(netmem)
+ << PAGE_SHIFT;
}
- page->dma_addr = addr;
+ netmem_set_dma_addr(netmem, addr);
return false;
}
diff --git a/include/trace/events/page_pool.h b/include/trace/events/page_pool.h
index 543e54e432a18..845c5f1f62f95 100644
--- a/include/trace/events/page_pool.h
+++ b/include/trace/events/page_pool.h
@@ -60,9 +60,9 @@ TRACE_EVENT(page_pool_state_release,
__entry->pfn = netmem_to_pfn(netmem);
),
- TP_printk("page_pool=%p netmem=%p pfn=0x%lx release=%u",
+ TP_printk("page_pool=%p netmem=%p is_net_iov=%lu pfn=0x%lx release=%u",
__entry->pool, (void *)__entry->netmem,
- __entry->pfn, __entry->release)
+ __entry->netmem & NET_IOV, __entry->pfn, __entry->release)
);
TRACE_EVENT(page_pool_state_hold,
@@ -86,9 +86,9 @@ TRACE_EVENT(page_pool_state_hold,
__entry->pfn = netmem_to_pfn(netmem);
),
- TP_printk("page_pool=%p netmem=%p pfn=0x%lx hold=%u",
+ TP_printk("page_pool=%p netmem=%p is_net_iov=%lu, pfn=0x%lx hold=%u",
__entry->pool, (void *)__entry->netmem,
- __entry->pfn, __entry->hold)
+ __entry->netmem & NET_IOV, __entry->pfn, __entry->hold)
);
TRACE_EVENT(page_pool_update_nid,
diff --git a/net/core/devmem.c b/net/core/devmem.c
index e0ec4e406467c..f573ad9e2cd10 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -80,7 +80,10 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
index = offset / PAGE_SIZE;
niov = &owner->niovs[index];
+ niov->pp_magic = 0;
+ niov->pp = NULL;
niov->dma_addr = 0;
+ atomic_long_set(&niov->pp_ref_count, 0);
net_devmem_dmabuf_binding_get(binding);
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 855271a6cad24..325ce1ec9007e 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -26,6 +26,8 @@
#include "page_pool_priv.h"
+DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers);
+
#define DEFER_TIME (msecs_to_jiffies(1000))
#define DEFER_WARN_INTERVAL (60 * HZ)
@@ -357,7 +359,7 @@ static noinline netmem_ref page_pool_refill_alloc_cache(struct page_pool *pool)
if (unlikely(!netmem))
break;
- if (likely(page_to_nid(netmem_to_page(netmem)) == pref_nid)) {
+ if (likely(netmem_is_pref_nid(netmem, pref_nid))) {
pool->alloc.cache[pool->alloc.count++] = netmem;
} else {
/* NUMA mismatch;
@@ -453,10 +455,8 @@ static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem)
static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
{
- struct page *page = netmem_to_page(netmem);
-
- page->pp = pool;
- page->pp_magic |= PP_SIGNATURE;
+ netmem_set_pp(netmem, pool);
+ netmem_or_pp_magic(netmem, PP_SIGNATURE);
/* Ensuring all pages have been split into one fragment initially:
* page_pool_set_pp_info() is only called once for every page when it
@@ -471,10 +471,8 @@ static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
static void page_pool_clear_pp_info(netmem_ref netmem)
{
- struct page *page = netmem_to_page(netmem);
-
- page->pp_magic = 0;
- page->pp = NULL;
+ netmem_clear_pp_magic(netmem);
+ netmem_set_pp(netmem, NULL);
}
static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
@@ -691,8 +689,9 @@ static bool page_pool_recycle_in_cache(netmem_ref netmem,
static bool __page_pool_page_can_be_recycled(netmem_ref netmem)
{
- return page_ref_count(netmem_to_page(netmem)) == 1 &&
- !page_is_pfmemalloc(netmem_to_page(netmem));
+ return netmem_is_net_iov(netmem) ||
+ (page_ref_count(netmem_to_page(netmem)) == 1 &&
+ !page_is_pfmemalloc(netmem_to_page(netmem)));
}
/* If the page refcnt == 1, this will try to recycle the page.
@@ -727,6 +726,7 @@ __page_pool_put_page(struct page_pool *pool, netmem_ref netmem,
/* Page found as candidate for recycling */
return netmem;
}
+
/* Fallback/non-XDP mode: API user have elevated refcnt.
*
* Many drivers split up the page into fragments, and some
@@ -948,7 +948,7 @@ static void page_pool_empty_ring(struct page_pool *pool)
/* Empty recycle ring */
while ((netmem = (__force netmem_ref)ptr_ring_consume_bh(&pool->ring))) {
/* Verify the refcnt invariant of cached pages */
- if (!(page_ref_count(netmem_to_page(netmem)) == 1))
+ if (!(netmem_ref_count(netmem) == 1))
pr_crit("%s() page_pool refcnt %d violation\n",
__func__, netmem_ref_count(netmem));
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 83f8cd8aa2d16..4c72b81dfcd95 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -917,9 +917,9 @@ static void skb_clone_fraglist(struct sk_buff *skb)
skb_get(list);
}
-static bool is_pp_page(struct page *page)
+static bool is_pp_netmem(netmem_ref netmem)
{
- return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
+ return (netmem_get_pp_magic(netmem) & ~0x3UL) == PP_SIGNATURE;
}
int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
@@ -1017,9 +1017,7 @@ EXPORT_SYMBOL(skb_cow_data_for_xdp);
#if IS_ENABLED(CONFIG_PAGE_POOL)
bool napi_pp_put_page(netmem_ref netmem)
{
- struct page *page = netmem_to_page(netmem);
-
- page = compound_head(page);
+ netmem = netmem_compound_head(netmem);
/* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
* in order to preserve any existing bits, such as bit 0 for the
@@ -1028,10 +1026,10 @@ bool napi_pp_put_page(netmem_ref netmem)
* and page_is_pfmemalloc() is checked in __page_pool_put_page()
* to avoid recycling the pfmemalloc page.
*/
- if (unlikely(!is_pp_page(page)))
+ if (unlikely(!is_pp_netmem(netmem)))
return false;
- page_pool_put_full_netmem(page->pp, page_to_netmem(page), false);
+ page_pool_put_full_netmem(netmem_get_pp(netmem), netmem, false);
return true;
}
@@ -1058,7 +1056,7 @@ static bool skb_pp_recycle(struct sk_buff *skb, void *data)
static int skb_pp_frag_ref(struct sk_buff *skb)
{
struct skb_shared_info *shinfo;
- struct page *head_page;
+ netmem_ref head_netmem;
int i;
if (!skb->pp_recycle)
@@ -1067,11 +1065,11 @@ static int skb_pp_frag_ref(struct sk_buff *skb)
shinfo = skb_shinfo(skb);
for (i = 0; i < shinfo->nr_frags; i++) {
- head_page = compound_head(skb_frag_page(&shinfo->frags[i]));
- if (likely(is_pp_page(head_page)))
- page_pool_ref_page(head_page);
+ head_netmem = netmem_compound_head(shinfo->frags[i].netmem);
+ if (likely(is_pp_netmem(head_netmem)))
+ page_pool_ref_netmem(head_netmem);
else
- page_ref_inc(head_page);
+ page_ref_inc(netmem_to_page(head_netmem));
}
return 0;
}
--
2.45.2.803.g4e1b14247a-goog