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[net-next,v8,04/10] net: psample: allow using rate as probability

Message ID 20240702095336.596506-5-amorenoz@redhat.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net: openvswitch: Add sample multicasting. | expand

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netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; GEN HAS DIFF 2 files changed, 274 insertions(+), 164 deletions(-);
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 839 this patch: 839
netdev/build_tools success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers success CCed 5 of 5 maintainers
netdev/build_clang success Errors and warnings before: 846 this patch: 846
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 853 this patch: 853
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 40 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-07-03--12-00 (tests: 666)

Commit Message

Adrian Moreno July 2, 2024, 9:53 a.m. UTC 
Although not explicitly documented in the psample module itself, the
definition of PSAMPLE_ATTR_SAMPLE_RATE seems inherited from act_sample.

Quoting tc-sample(8):
"RATE of 100 will lead to an average of one sampled packet out of every
100 observed."

With this semantics, the rates that we can express with an unsigned
32-bits number are very unevenly distributed and concentrated towards
"sampling few packets".
For example, we can express a probability of 2.32E-8% but we
cannot express anything between 100% and 50%.

For sampling applications that are capable of sampling a decent
amount of packets, this sampling rate semantics is not very useful.

Add a new flag to the uAPI that indicates that the sampling rate is
expressed in scaled probability, this is:
- 0 is 0% probability, no packets get sampled.
- U32_MAX is 100% probability, all packets get sampled.

Reviewed-by: Aaron Conole <aconole@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
---
 include/net/psample.h        |  3 ++-
 include/uapi/linux/psample.h | 10 +++++++++-
 net/psample/psample.c        |  3 +++
 3 files changed, 14 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/include/net/psample.h b/include/net/psample.h
index 2ac71260a546..c52e9ebd88dd 100644
--- a/include/net/psample.h
+++ b/include/net/psample.h
@@ -24,7 +24,8 @@  struct psample_metadata {
 	u8 out_tc_valid:1,
 	   out_tc_occ_valid:1,
 	   latency_valid:1,
-	   unused:5;
+	   rate_as_probability:1,
+	   unused:4;
 	const u8 *user_cookie;
 	u32 user_cookie_len;
 };
diff --git a/include/uapi/linux/psample.h b/include/uapi/linux/psample.h
index e80637e1d97b..b765f0e81f20 100644
--- a/include/uapi/linux/psample.h
+++ b/include/uapi/linux/psample.h
@@ -8,7 +8,11 @@  enum {
 	PSAMPLE_ATTR_ORIGSIZE,
 	PSAMPLE_ATTR_SAMPLE_GROUP,
 	PSAMPLE_ATTR_GROUP_SEQ,
-	PSAMPLE_ATTR_SAMPLE_RATE,
+	PSAMPLE_ATTR_SAMPLE_RATE,	/* u32, ratio between observed and
+					 * sampled packets or scaled probability
+					 * if PSAMPLE_ATTR_SAMPLE_PROBABILITY
+					 * is set.
+					 */
 	PSAMPLE_ATTR_DATA,
 	PSAMPLE_ATTR_GROUP_REFCOUNT,
 	PSAMPLE_ATTR_TUNNEL,
@@ -20,6 +24,10 @@  enum {
 	PSAMPLE_ATTR_TIMESTAMP,		/* u64, nanoseconds */
 	PSAMPLE_ATTR_PROTO,		/* u16 */
 	PSAMPLE_ATTR_USER_COOKIE,	/* binary, user provided data */
+	PSAMPLE_ATTR_SAMPLE_PROBABILITY,/* no argument, interpret rate in
+					 * PSAMPLE_ATTR_SAMPLE_RATE as a
+					 * probability scaled 0 - U32_MAX.
+					 */
 
 	__PSAMPLE_ATTR_MAX
 };
diff --git a/net/psample/psample.c b/net/psample/psample.c
index 1c76f3e48dcd..f48b5b9cd409 100644
--- a/net/psample/psample.c
+++ b/net/psample/psample.c
@@ -497,6 +497,9 @@  void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
 		    md->user_cookie))
 		goto error;
 
+	if (md->rate_as_probability)
+		nla_put_flag(skb, PSAMPLE_ATTR_SAMPLE_PROBABILITY);
+
 	genlmsg_end(nl_skb, data);
 	genlmsg_multicast_netns(&psample_nl_family, group->net, nl_skb, 0,
 				PSAMPLE_NL_MCGRP_SAMPLE, GFP_ATOMIC);