Re: [ovs-dev] [PATCH net-next v2 4/9] net: psample: allow using rate as probability
On Mon, Jun 17, 2024 at 06:32:14AM +, Adrián Moreno wrote: > On Fri, Jun 14, 2024 at 05:11:30PM GMT, Simon Horman wrote: > > On Mon, Jun 03, 2024 at 08:56:38PM +0200, Adrian Moreno wrote: > > > 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. > > > > > > Signed-off-by: Adrian Moreno > > > > Hi Adrian, > > > > Would it be possible to add appropriate documentation for > > rate - both the original ratio variant, and the new probability > > variant - somewhere? > > > > Hi Simon, thanks for the suggestion. Would the uapi header be a good > place for such documentation? Hi Adrian, I didn't look closely, but that does sound like a good place to me. ___ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
Re: [ovs-dev] [PATCH net-next v2 4/9] net: psample: allow using rate as probability
On Fri, Jun 14, 2024 at 05:11:30PM GMT, Simon Horman wrote: > On Mon, Jun 03, 2024 at 08:56:38PM +0200, Adrian Moreno wrote: > > 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. > > > > Signed-off-by: Adrian Moreno > > Hi Adrian, > > Would it be possible to add appropriate documentation for > rate - both the original ratio variant, and the new probability > variant - somewhere? > Hi Simon, thanks for the suggestion. Would the uapi header be a good place for such documentation? > That aside, this looks good to me. > > ... > ___ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
Re: [ovs-dev] [PATCH net-next v2 4/9] net: psample: allow using rate as probability
On Mon, Jun 03, 2024 at 08:56:38PM +0200, Adrian Moreno wrote: > 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. > > Signed-off-by: Adrian Moreno Hi Adrian, Would it be possible to add appropriate documentation for rate - both the original ratio variant, and the new probability variant - somewhere? That aside, this looks good to me. ... ___ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
[ovs-dev] [PATCH net-next v2 4/9] net: psample: allow using rate as probability
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.
Signed-off-by: Adrian Moreno
---
include/net/psample.h | 3 ++-
include/uapi/linux/psample.h | 4
include/uapi/linux/tc_act/tc_sample.h | 1 +
net/psample/psample.c | 3 +++
4 files changed, 10 insertions(+), 1 deletion(-)
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..8b069e75beab 100644
--- a/include/uapi/linux/psample.h
+++ b/include/uapi/linux/psample.h
@@ -20,6 +20,10 @@ 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/include/uapi/linux/tc_act/tc_sample.h
b/include/uapi/linux/tc_act/tc_sample.h
index fee1bcc20793..7ee0735e7b38 100644
--- a/include/uapi/linux/tc_act/tc_sample.h
+++ b/include/uapi/linux/tc_act/tc_sample.h
@@ -18,6 +18,7 @@ enum {
TCA_SAMPLE_TRUNC_SIZE,
TCA_SAMPLE_PSAMPLE_GROUP,
TCA_SAMPLE_PAD,
+ TCA_SAMPLE_PROBABILITY,
__TCA_SAMPLE_MAX
};
#define TCA_SAMPLE_MAX (__TCA_SAMPLE_MAX - 1)
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(_nl_family, group->net, nl_skb, 0,
PSAMPLE_NL_MCGRP_SAMPLE, GFP_ATOMIC);
--
2.45.1
___
dev mailing list
d...@openvswitch.org
https://mail.openvswitch.org/mailman/listinfo/ovs-dev
