On 12/28/2015 01:55 PM, Ming Lei wrote:
Both htab_map_update_elem() and htab_map_delete_elem() can be
called from eBPF program, and they may be in kernel hot path,
so it isn't efficient to use a per-hashtable lock in this two
helpers.
The per-hashtable spinlock is used for protecting bucket's
hlist, and per-bucket lock is just enough. This patch converts
the per-hashtable lock into per-bucket spinlock, so that
contention can be decreased a lot.
Signed-off-by: Ming Lei <tom.leim...@gmail.com>
---
kernel/bpf/hashtab.c | 46 ++++++++++++++++++++++++++++++----------------
1 file changed, 30 insertions(+), 16 deletions(-)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index d857fcb..67222a9 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -14,10 +14,14 @@
#include <linux/filter.h>
#include <linux/vmalloc.h>
+struct bucket {
+ struct hlist_head head;
+ raw_spinlock_t lock;
+};
+
struct bpf_htab {
struct bpf_map map;
- struct hlist_head *buckets;
- raw_spinlock_t lock;
+ struct bucket *buckets;
atomic_t count; /* number of elements in this hashtable */
u32 n_buckets; /* number of hash buckets */
u32 elem_size; /* size of each element in bytes */
@@ -88,24 +92,25 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
/* make sure page count doesn't overflow */
goto free_htab;
When adapting memory accounting and allocation sizes below where you replace
sizeof(struct hlist_head) with sizeof(struct bucket), is there a reason why
you don't update the overflow checks along with it?
[...]
/* prevent zero size kmalloc and check for u32 overflow */
if (htab->n_buckets == 0 ||
htab->n_buckets > U32_MAX / sizeof(struct hlist_head))
goto free_htab;
if ((u64) htab->n_buckets * sizeof(struct hlist_head) +
(u64) htab->elem_size * htab->map.max_entries >=
U32_MAX - PAGE_SIZE)
/* make sure page count doesn't overflow */
goto free_htab;
[...]
- htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
+ htab->map.pages = round_up(htab->n_buckets * sizeof(struct bucket) +
htab->elem_size * htab->map.max_entries,
PAGE_SIZE) >> PAGE_SHIFT;
err = -ENOMEM;
- htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct
hlist_head),
+ htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
GFP_USER | __GFP_NOWARN);
if (!htab->buckets) {
- htab->buckets = vmalloc(htab->n_buckets * sizeof(struct
hlist_head));
+ htab->buckets = vmalloc(htab->n_buckets * sizeof(struct
bucket));
if (!htab->buckets)
goto free_htab;
}
[...]
Thanks,
Daniel
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
