Author: adrian
Date: Tue May 27 08:06:20 2014
New Revision: 266737
URL: http://svnweb.freebsd.org/changeset/base/266737
Log:
The users of RSS shouldn't be directly concerned about hash -> CPU ID
mappings. Instead, they should be first mapping to an RSS bucket and
then querying the RSS bucket -> CPU ID mapping to figure out the target
CPU.
When (if?) RSS rebalancing is implemented or some other (non round-robin)
distribution of work from buckets to CPU IDs, various bits of code - both
userland and kernel - will need to know how this mapping works.
So, to support this:
* Add a new function rss_m2bucket() - this maps an mbuf to a given bucket.
Anything which is currently doing hash -> CPU work may instead wish to
do hash -> bucket, and then query the bucket->cpuid map for which
CPU it belongs on. Or, map it to a bucket, then re-pin that bucket ->
CPU during a rebalance operation.
* For userland applications which wish to exploit affinity to RSS buckets,
the bucket -> CPU ID mapping is now available via a sysctl.
net.inet.rss.bucket_mapping lists the bucket to CPU ID mapping via
a list of bucket:cpu pairs.
Modified:
head/sys/netinet/in_rss.c
head/sys/netinet/in_rss.h
Modified: head/sys/netinet/in_rss.c
==============================================================================
--- head/sys/netinet/in_rss.c Tue May 27 07:16:43 2014 (r266736)
+++ head/sys/netinet/in_rss.c Tue May 27 08:06:20 2014 (r266737)
@@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
#include <sys/kernel.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
+#include <sys/sbuf.h>
#include <net/if.h>
#include <net/if_var.h>
@@ -425,6 +426,24 @@ rss_hash2cpuid(uint32_t hash_val, uint32
}
/*
+ * Query the RSS bucket associated with the given hash value and
+ * type.
+ */
+int
+rss_hash2bucket(uint32_t hash_val, uint32_t hash_type, uint32_t *bucket_id)
+{
+
+ switch (hash_type) {
+ case M_HASHTYPE_RSS_IPV4:
+ case M_HASHTYPE_RSS_TCP_IPV4:
+ *bucket_id = rss_getbucket(hash_val);
+ return (0);
+ default:
+ return (-1);
+ }
+}
+
+/*
* netisr CPU affinity lookup routine for use by protocols.
*/
struct mbuf *
@@ -436,6 +455,16 @@ rss_m2cpuid(struct mbuf *m, uintptr_t so
return (m);
}
+int
+rss_m2bucket(struct mbuf *m, uint32_t *bucket_id)
+{
+
+ M_ASSERTPKTHDR(m);
+
+ return(rss_hash2bucket(m->m_pkthdr.flowid, M_HASHTYPE_GET(m),
+ bucket_id));
+}
+
/*
* Query the RSS hash algorithm.
*/
@@ -512,3 +541,31 @@ sysctl_rss_key(SYSCTL_HANDLER_ARGS)
SYSCTL_PROC(_net_inet_rss, OID_AUTO, key,
CTLTYPE_OPAQUE | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, sysctl_rss_key,
"", "RSS keying material");
+
+static int
+sysctl_rss_bucket_mapping(SYSCTL_HANDLER_ARGS)
+{
+ struct sbuf *sb;
+ int error;
+ int i;
+
+ error = 0;
+ error = sysctl_wire_old_buffer(req, 0);
+ if (error != 0)
+ return (error);
+ sb = sbuf_new_for_sysctl(NULL, NULL, 512, req);
+ if (sb == NULL)
+ return (ENOMEM);
+ for (i = 0; i < rss_buckets; i++) {
+ sbuf_printf(sb, "%s%d:%d", i == 0 ? "" : " ",
+ i,
+ rss_getcpu(i));
+ }
+ error = sbuf_finish(sb);
+ sbuf_delete(sb);
+
+ return (error);
+}
+SYSCTL_PROC(_net_inet_rss, OID_AUTO, bucket_mapping,
+ CTLTYPE_STRING | CTLFLAG_RD, NULL, 0,
+ sysctl_rss_bucket_mapping, "", "RSS bucket -> CPU mapping");
Modified: head/sys/netinet/in_rss.h
==============================================================================
--- head/sys/netinet/in_rss.h Tue May 27 07:16:43 2014 (r266736)
+++ head/sys/netinet/in_rss.h Tue May 27 08:06:20 2014 (r266737)
@@ -91,5 +91,8 @@ uint32_t rss_hash_ip6_2tuple(struct in6_
*/
struct mbuf *rss_m2cpuid(struct mbuf *m, uintptr_t source, u_int *cpuid);
u_int rss_hash2cpuid(uint32_t hash_val, uint32_t hash_type);
+int rss_hash2bucket(uint32_t hash_val, uint32_t hash_type,
+ uint32_t *bucket_id);
+int rss_m2bucket(struct mbuf *m, uint32_t *bucket_id);
#endif /* !_NETINET_IN_RSS_H_ */
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