From 115f1a5c42bdad9a9ea356fc0b4a39ec7537947f Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 6 Feb 2023 17:31:00 +0000
Subject: [PATCH 1/4] net: add SKB_HEAD_ALIGN() helper
We have many places using this expression:
SKB_DATA_ALIGN(sizeof(struct skb_shared_info))
Use of SKB_HEAD_ALIGN() will allow to clean them.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
include/linux/skbuff.h | 8 ++++++++
net/core/skbuff.c | 18 ++++++------------
2 files changed, 14 insertions(+), 12 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 1fa95b916342e..c3df3b55da976 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -255,6 +255,14 @@
#define SKB_DATA_ALIGN(X) ALIGN(X, SMP_CACHE_BYTES)
#define SKB_WITH_OVERHEAD(X) \
((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
+/* For X bytes available in skb->head, what is the minimal
+ * allocation needed, knowing struct skb_shared_info needs
+ * to be aligned.
+ */
+#define SKB_HEAD_ALIGN(X) (SKB_DATA_ALIGN(X) + \
+ SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
#define SKB_MAX_ORDER(X, ORDER) \
SKB_WITH_OVERHEAD((PAGE_SIZE << (ORDER)) - (X))
#define SKB_MAX_HEAD(X) (SKB_MAX_ORDER((X), 0))
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 624e9e4ec116e..4abfc3ba6898d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -558,8 +558,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* aligned memory blocks, unless SLUB/SLAB debug is enabled.
* Both skb->head and skb_shared_info are cache line aligned.
*/
- size = SKB_DATA_ALIGN(size);
- size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+ size = SKB_HEAD_ALIGN(size);
osize = kmalloc_size_roundup(size);
data = kmalloc_reserve(osize, gfp_mask, node, &pfmemalloc);
if (unlikely(!data))
@@ -632,8 +631,7 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
goto skb_success;
}
- len += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- len = SKB_DATA_ALIGN(len);
+ len = SKB_HEAD_ALIGN(len);
if (sk_memalloc_socks())
gfp_mask |= __GFP_MEMALLOC;
@@ -732,8 +730,7 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
data = page_frag_alloc_1k(&nc->page_small, gfp_mask);
pfmemalloc = NAPI_SMALL_PAGE_PFMEMALLOC(nc->page_small);
} else {
- len += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- len = SKB_DATA_ALIGN(len);
+ len = SKB_HEAD_ALIGN(len);
data = page_frag_alloc(&nc->page, len, gfp_mask);
pfmemalloc = nc->page.pfmemalloc;
@@ -1938,8 +1935,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;
- size = SKB_DATA_ALIGN(size);
- size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+ size = SKB_HEAD_ALIGN(size);
size = kmalloc_size_roundup(size);
data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
if (!data)
@@ -6289,8 +6285,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;
- size = SKB_DATA_ALIGN(size);
- size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+ size = SKB_HEAD_ALIGN(size);
size = kmalloc_size_roundup(size);
data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
if (!data)
@@ -6408,8 +6403,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;
- size = SKB_DATA_ALIGN(size);
- size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+ size = SKB_HEAD_ALIGN(size);
size = kmalloc_size_roundup(size);
data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
if (!data)
From 65998d2bf857b9ae5acc1f3b70892bd1b429ccab Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 6 Feb 2023 17:31:01 +0000
Subject: [PATCH 2/4] net: remove osize variable in __alloc_skb()
This is a cleanup patch, to prepare following change.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/core/skbuff.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4abfc3ba6898d..333f793f9cdba 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -533,7 +533,6 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
{
struct kmem_cache *cache;
struct sk_buff *skb;
- unsigned int osize;
bool pfmemalloc;
u8 *data;
@@ -559,16 +558,15 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* Both skb->head and skb_shared_info are cache line aligned.
*/
size = SKB_HEAD_ALIGN(size);
- osize = kmalloc_size_roundup(size);
- data = kmalloc_reserve(osize, gfp_mask, node, &pfmemalloc);
+ size = kmalloc_size_roundup(size);
+ data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc);
if (unlikely(!data))
goto nodata;
/* kmalloc_size_roundup() might give us more room than requested.
* Put skb_shared_info exactly at the end of allocated zone,
* to allow max possible filling before reallocation.
*/
- size = SKB_WITH_OVERHEAD(osize);
- prefetchw(data + size);
+ prefetchw(data + SKB_WITH_OVERHEAD(size));
/*
* Only clear those fields we need to clear, not those that we will
@@ -576,7 +574,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* the tail pointer in struct sk_buff!
*/
memset(skb, 0, offsetof(struct sk_buff, tail));
- __build_skb_around(skb, data, osize);
+ __build_skb_around(skb, data, size);
skb->pfmemalloc = pfmemalloc;
if (flags & SKB_ALLOC_FCLONE) {
From 5c0e820cbbbe2d1c4cea5cd2bfc1302c123436df Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 6 Feb 2023 17:31:02 +0000
Subject: [PATCH 3/4] net: factorize code in kmalloc_reserve()
All kmalloc_reserve() callers have to make the same computation,
we can factorize them, to prepare following patch in the series.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/core/skbuff.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 333f793f9cdba..c1232837cd0cb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -478,17 +478,20 @@ EXPORT_SYMBOL(napi_build_skb);
* may be used. Otherwise, the packet data may be discarded until enough
* memory is free
*/
-static void *kmalloc_reserve(size_t size, gfp_t flags, int node,
+static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
bool *pfmemalloc)
{
- void *obj;
bool ret_pfmemalloc = false;
+ unsigned int obj_size;
+ void *obj;
+ obj_size = SKB_HEAD_ALIGN(*size);
+ *size = obj_size = kmalloc_size_roundup(obj_size);
/*
* Try a regular allocation, when that fails and we're not entitled
* to the reserves, fail.
*/
- obj = kmalloc_node_track_caller(size,
+ obj = kmalloc_node_track_caller(obj_size,
flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
node);
if (obj || !(gfp_pfmemalloc_allowed(flags)))
@@ -496,7 +499,7 @@ static void *kmalloc_reserve(size_t size, gfp_t flags, int node,
/* Try again but now we are using pfmemalloc reserves */
ret_pfmemalloc = true;
- obj = kmalloc_node_track_caller(size, flags, node);
+ obj = kmalloc_node_track_caller(obj_size, flags, node);
out:
if (pfmemalloc)
@@ -557,9 +560,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
* aligned memory blocks, unless SLUB/SLAB debug is enabled.
* Both skb->head and skb_shared_info are cache line aligned.
*/
- size = SKB_HEAD_ALIGN(size);
- size = kmalloc_size_roundup(size);
- data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc);
+ data = kmalloc_reserve(&size, gfp_mask, node, &pfmemalloc);
if (unlikely(!data))
goto nodata;
/* kmalloc_size_roundup() might give us more room than requested.
@@ -1933,9 +1934,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;
- size = SKB_HEAD_ALIGN(size);
- size = kmalloc_size_roundup(size);
- data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
+ data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
if (!data)
goto nodata;
size = SKB_WITH_OVERHEAD(size);
@@ -6283,9 +6282,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;
- size = SKB_HEAD_ALIGN(size);
- size = kmalloc_size_roundup(size);
- data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
+ data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
if (!data)
return -ENOMEM;
size = SKB_WITH_OVERHEAD(size);
@@ -6401,9 +6398,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
if (skb_pfmemalloc(skb))
gfp_mask |= __GFP_MEMALLOC;
- size = SKB_HEAD_ALIGN(size);
- size = kmalloc_size_roundup(size);
- data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
+ data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
if (!data)
return -ENOMEM;
size = SKB_WITH_OVERHEAD(size);
From bf9f1baa279f0758dc2297080360c5a616843927 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 6 Feb 2023 17:31:03 +0000
Subject: [PATCH 4/4] net: add dedicated kmem_cache for typical/small skb->head
Recent removal of ksize() in alloc_skb() increased
performance because we no longer read
the associated struct page.
We have an equivalent cost at kfree_skb() time.
kfree(skb->head) has to access a struct page,
often cold in cpu caches to get the owning
struct kmem_cache.
Considering that many allocations are small (at least for TCP ones)
we can have our own kmem_cache to avoid the cache line miss.
This also saves memory because these small heads
are no longer padded to 1024 bytes.
CONFIG_SLUB=y
$ grep skbuff_small_head /proc/slabinfo
skbuff_small_head 2907 2907 640 51 8 : tunables 0 0 0 : slabdata 57 57 0
CONFIG_SLAB=y
$ grep skbuff_small_head /proc/slabinfo
skbuff_small_head 607 624 640 6 1 : tunables 54 27 8 : slabdata 104 104 5
Notes:
- After Kees Cook patches and this one, we might
be able to revert commit
dbae2b062824 ("net: skb: introduce and use a single page frag cache")
because GRO_MAX_HEAD is also small.
- This patch is a NOP for CONFIG_SLOB=y builds.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/core/skbuff.c | 72 +++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 67 insertions(+), 5 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c1232837cd0cb..bdb1e015e32b9 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -89,6 +89,34 @@ static struct kmem_cache *skbuff_fclone_cache __ro_after_init;
#ifdef CONFIG_SKB_EXTENSIONS
static struct kmem_cache *skbuff_ext_cache __ro_after_init;
#endif
+
+/* skb_small_head_cache and related code is only supported
+ * for CONFIG_SLAB and CONFIG_SLUB.
+ * As soon as SLOB is removed from the kernel, we can clean up this.
+ */
+#if !defined(CONFIG_SLOB)
+# define HAVE_SKB_SMALL_HEAD_CACHE 1
+#endif
+
+#ifdef HAVE_SKB_SMALL_HEAD_CACHE
+static struct kmem_cache *skb_small_head_cache __ro_after_init;
+
+#define SKB_SMALL_HEAD_SIZE SKB_HEAD_ALIGN(MAX_TCP_HEADER)
+
+/* We want SKB_SMALL_HEAD_CACHE_SIZE to not be a power of two.
+ * This should ensure that SKB_SMALL_HEAD_HEADROOM is a unique
+ * size, and we can differentiate heads from skb_small_head_cache
+ * vs system slabs by looking at their size (skb_end_offset()).
+ */
+#define SKB_SMALL_HEAD_CACHE_SIZE \
+ (is_power_of_2(SKB_SMALL_HEAD_SIZE) ? \
+ (SKB_SMALL_HEAD_SIZE + L1_CACHE_BYTES) : \
+ SKB_SMALL_HEAD_SIZE)
+
+#define SKB_SMALL_HEAD_HEADROOM \
+ SKB_WITH_OVERHEAD(SKB_SMALL_HEAD_CACHE_SIZE)
+#endif /* HAVE_SKB_SMALL_HEAD_CACHE */
+
int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;
EXPORT_SYMBOL(sysctl_max_skb_frags);
@@ -486,6 +514,23 @@ static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
void *obj;
obj_size = SKB_HEAD_ALIGN(*size);
+#ifdef HAVE_SKB_SMALL_HEAD_CACHE
+ if (obj_size <= SKB_SMALL_HEAD_CACHE_SIZE &&
+ !(flags & KMALLOC_NOT_NORMAL_BITS)) {
+
+ /* skb_small_head_cache has non power of two size,
+ * likely forcing SLUB to use order-3 pages.
+ * We deliberately attempt a NOMEMALLOC allocation only.
+ */
+ obj = kmem_cache_alloc_node(skb_small_head_cache,
+ flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
+ node);
+ if (obj) {
+ *size = SKB_SMALL_HEAD_CACHE_SIZE;
+ goto out;
+ }
+ }
+#endif
*size = obj_size = kmalloc_size_roundup(obj_size);
/*
* Try a regular allocation, when that fails and we're not entitled
@@ -805,6 +850,16 @@ static bool skb_pp_recycle(struct sk_buff *skb, void *data)
return page_pool_return_skb_page(virt_to_page(data));
}
+static void skb_kfree_head(void *head, unsigned int end_offset)
+{
+#ifdef HAVE_SKB_SMALL_HEAD_CACHE
+ if (end_offset == SKB_SMALL_HEAD_HEADROOM)
+ kmem_cache_free(skb_small_head_cache, head);
+ else
+#endif
+ kfree(head);
+}
+
static void skb_free_head(struct sk_buff *skb)
{
unsigned char *head = skb->head;
@@ -814,7 +869,7 @@ static void skb_free_head(struct sk_buff *skb)
return;
skb_free_frag(head);
} else {
- kfree(head);
+ skb_kfree_head(head, skb_end_offset(skb));
}
}
@@ -1997,7 +2052,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
return 0;
nofrags:
- kfree(data);
+ skb_kfree_head(data, size);
nodata:
return -ENOMEM;
}
@@ -4634,6 +4689,13 @@ void __init skb_init(void)
0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC,
NULL);
+#ifdef HAVE_SKB_SMALL_HEAD_CACHE
+ skb_small_head_cache = kmem_cache_create("skbuff_small_head",
+ SKB_SMALL_HEAD_CACHE_SIZE,
+ 0,
+ SLAB_HWCACHE_ALIGN | SLAB_PANIC,
+ NULL);
+#endif
skb_extensions_init();
}
@@ -6298,7 +6360,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
if (skb_cloned(skb)) {
/* drop the old head gracefully */
if (skb_orphan_frags(skb, gfp_mask)) {
- kfree(data);
+ skb_kfree_head(data, size);
return -ENOMEM;
}
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
@@ -6406,7 +6468,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
memcpy((struct skb_shared_info *)(data + size),
skb_shinfo(skb), offsetof(struct skb_shared_info, frags[0]));
if (skb_orphan_frags(skb, gfp_mask)) {
- kfree(data);
+ skb_kfree_head(data, size);
return -ENOMEM;
}
shinfo = (struct skb_shared_info *)(data + size);
@@ -6442,7 +6504,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
/* skb_frag_unref() is not needed here as shinfo->nr_frags = 0. */
if (skb_has_frag_list(skb))
kfree_skb_list(skb_shinfo(skb)->frag_list);
- kfree(data);
+ skb_kfree_head(data, size);
return -ENOMEM;
}
skb_release_data(skb, SKB_CONSUMED);