| Message ID | 20200617174226.2301909-1-kafai@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next] bpf: sk_storage: Prefer to get a free cache_idx | expand |
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>
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
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; }
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(-)