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* [PATCH bpf-next] bpf: sk_storage: Prefer to get a free cache_idx
@ 2020-06-17 17:42 Martin KaFai Lau
  2020-06-18  5:01 ` John Fastabend
  0 siblings, 1 reply; 3+ messages in thread
From: Martin KaFai Lau @ 2020-06-17 17:42 UTC (permalink / raw)
  To: bpf; +Cc: Alexei Starovoitov, Daniel Borkmann, kernel-team, netdev

The cache_idx is currently picked by RR.  There is chance that
the same cache_idx will be picked by multiple sk_storage_maps while
other cache_idx is still unused.  e.g. It could happen when the
sk_storage_map is recreated during the restart of the user
space process.

This patch tracks the usage count for each cache_idx.  There is
16 of them now (defined in BPF_SK_STORAGE_CACHE_SIZE).
It will try to pick the free cache_idx.  If none was found,
it would pick one with the minimal usage count.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 net/core/bpf_sk_storage.c | 41 +++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index d2c4d16dadba..1dae4b543243 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -11,8 +11,6 @@
 #include <uapi/linux/sock_diag.h>
 #include <uapi/linux/btf.h>
 
-static atomic_t cache_idx;
-
 #define SK_STORAGE_CREATE_FLAG_MASK					\
 	(BPF_F_NO_PREALLOC | BPF_F_CLONE)
 
@@ -81,6 +79,9 @@ struct bpf_sk_storage_elem {
 #define SDATA(_SELEM) (&(_SELEM)->sdata)
 #define BPF_SK_STORAGE_CACHE_SIZE	16
 
+static DEFINE_SPINLOCK(cache_idx_lock);
+static u64 cache_idx_usage_counts[BPF_SK_STORAGE_CACHE_SIZE];
+
 struct bpf_sk_storage {
 	struct bpf_sk_storage_data __rcu *cache[BPF_SK_STORAGE_CACHE_SIZE];
 	struct hlist_head list;	/* List of bpf_sk_storage_elem */
@@ -512,6 +513,37 @@ static int sk_storage_delete(struct sock *sk, struct bpf_map *map)
 	return 0;
 }
 
+static u16 cache_idx_get(void)
+{
+	u64 min_usage = U64_MAX;
+	u16 i, res = 0;
+
+	spin_lock(&cache_idx_lock);
+
+	for (i = 0; i < BPF_SK_STORAGE_CACHE_SIZE; i++) {
+		if (cache_idx_usage_counts[i] < min_usage) {
+			min_usage = cache_idx_usage_counts[i];
+			res = i;
+
+			/* Found a free cache_idx */
+			if (!min_usage)
+				break;
+		}
+	}
+	cache_idx_usage_counts[res]++;
+
+	spin_unlock(&cache_idx_lock);
+
+	return res;
+}
+
+static void cache_idx_free(u16 idx)
+{
+	spin_lock(&cache_idx_lock);
+	cache_idx_usage_counts[idx]--;
+	spin_unlock(&cache_idx_lock);
+}
+
 /* Called by __sk_destruct() & bpf_sk_storage_clone() */
 void bpf_sk_storage_free(struct sock *sk)
 {
@@ -560,6 +592,8 @@ static void bpf_sk_storage_map_free(struct bpf_map *map)
 
 	smap = (struct bpf_sk_storage_map *)map;
 
+	cache_idx_free(smap->cache_idx);
+
 	/* Note that this map might be concurrently cloned from
 	 * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
 	 * RCU read section to finish before proceeding. New RCU
@@ -673,8 +707,7 @@ static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr)
 	}
 
 	smap->elem_size = sizeof(struct bpf_sk_storage_elem) + attr->value_size;
-	smap->cache_idx = (unsigned int)atomic_inc_return(&cache_idx) %
-		BPF_SK_STORAGE_CACHE_SIZE;
+	smap->cache_idx = cache_idx_get();
 
 	return &smap->map;
 }
-- 
2.24.1


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* RE: [PATCH bpf-next] bpf: sk_storage: Prefer to get a free cache_idx
  2020-06-17 17:42 [PATCH bpf-next] bpf: sk_storage: Prefer to get a free cache_idx Martin KaFai Lau
@ 2020-06-18  5:01 ` John Fastabend
  2020-06-18 21:48   ` Alexei Starovoitov
  0 siblings, 1 reply; 3+ messages in thread
From: John Fastabend @ 2020-06-18  5:01 UTC (permalink / raw)
  To: Martin KaFai Lau, bpf
  Cc: Alexei Starovoitov, Daniel Borkmann, kernel-team, netdev

Martin KaFai Lau wrote:
> The cache_idx is currently picked by RR.  There is chance that
> the same cache_idx will be picked by multiple sk_storage_maps while
> other cache_idx is still unused.  e.g. It could happen when the
> sk_storage_map is recreated during the restart of the user
> space process.
> 
> This patch tracks the usage count for each cache_idx.  There is
> 16 of them now (defined in BPF_SK_STORAGE_CACHE_SIZE).
> It will try to pick the free cache_idx.  If none was found,
> it would pick one with the minimal usage count.
> 
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> ---
>  net/core/bpf_sk_storage.c | 41 +++++++++++++++++++++++++++++++++++----
>  1 file changed, 37 insertions(+), 4 deletions(-)
> 

Acked-by: John Fastabend <john.fastabend@gmail.com>

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH bpf-next] bpf: sk_storage: Prefer to get a free cache_idx
  2020-06-18  5:01 ` John Fastabend
@ 2020-06-18 21:48   ` Alexei Starovoitov
  0 siblings, 0 replies; 3+ messages in thread
From: Alexei Starovoitov @ 2020-06-18 21:48 UTC (permalink / raw)
  To: John Fastabend
  Cc: Martin KaFai Lau, bpf, Alexei Starovoitov, Daniel Borkmann,
	Kernel Team, Network Development

On Wed, Jun 17, 2020 at 10:01 PM John Fastabend
<john.fastabend@gmail.com> wrote:
>
> Martin KaFai Lau wrote:
> > The cache_idx is currently picked by RR.  There is chance that
> > the same cache_idx will be picked by multiple sk_storage_maps while
> > other cache_idx is still unused.  e.g. It could happen when the
> > sk_storage_map is recreated during the restart of the user
> > space process.
> >
> > This patch tracks the usage count for each cache_idx.  There is
> > 16 of them now (defined in BPF_SK_STORAGE_CACHE_SIZE).
> > It will try to pick the free cache_idx.  If none was found,
> > it would pick one with the minimal usage count.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > ---
> >  net/core/bpf_sk_storage.c | 41 +++++++++++++++++++++++++++++++++++----
> >  1 file changed, 37 insertions(+), 4 deletions(-)
> >
>
> Acked-by: John Fastabend <john.fastabend@gmail.com>

Applied. Thanks

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2020-06-18 21:49 UTC | newest]

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2020-06-17 17:42 [PATCH bpf-next] bpf: sk_storage: Prefer to get a free cache_idx Martin KaFai Lau
2020-06-18  5:01 ` John Fastabend
2020-06-18 21:48   ` Alexei Starovoitov

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