pespin has submitted this change. (
https://gerrit.osmocom.org/c/osmo-bts/+/17766 )
Change subject: osmo-bts-trx: Use much lower clock advance values towards PCU
and TRX
......................................................................
osmo-bts-trx: Use much lower clock advance values towards PCU and TRX
osmotrx fn-advance (which is the clock_advance variable here) and
osmotrx rts-advance together make up the minimum delay the BTS can react
to a channel request, etc.
The default of 20 are around 92ms which is clearly too much. With
modern hardware and using SCHED_RR a lower value should not be an issue.
See OS#4487 for some related measurements on more CPU-limited devices like a
LimeNet-micro3.
Fixes: OS#4487
Fixes: SYS#4885
Related: SYS#4881
Change-Id: I7da3d0948f38e12342fb714b29f8edc5e9d0933d
---
M doc/manuals/chapters/bts-models.adoc
M src/osmo-bts-trx/main.c
2 files changed, 4 insertions(+), 5 deletions(-)
Approvals:
Jenkins Builder: Verified
fixeria: Looks good to me, but someone else must approve
daniel: Looks good to me, but someone else must approve
pespin: Looks good to me, approved
diff --git a/doc/manuals/chapters/bts-models.adoc
b/doc/manuals/chapters/bts-models.adoc
index 495571f..5cb0461 100644
--- a/doc/manuals/chapters/bts-models.adoc
+++ b/doc/manuals/chapters/bts-models.adoc
@@ -270,8 +270,7 @@
running it on the same machine, where the UDP packets are just passed
over the loopback device.
-The default value for `fn-advance` is 20 (corresponding to 92
-milliseconds).
+The default value for `fn-advance` is 2 (corresponding to 9.2 milliseconds).
===== `osmotrx rts-advance <0-30>`
@@ -290,7 +289,7 @@
N + fn-advance + rts-advance
-The default value of `rts-advance` is 5 (corresponding to 23 milliseconds).
+The default value of `rts-advance` is 3 (corresponding to 14 milliseconds).
Do not change this unless you have a good reason!
===== `osmotrx rx-gain <0-50>`
diff --git a/src/osmo-bts-trx/main.c b/src/osmo-bts-trx/main.c
index 33bc6f2..166af7e 100644
--- a/src/osmo-bts-trx/main.c
+++ b/src/osmo-bts-trx/main.c
@@ -167,8 +167,8 @@
plink->u.osmotrx.remote_ip = talloc_strdup(plink, "127.0.0.1");
plink->u.osmotrx.base_port_local = 5800;
plink->u.osmotrx.base_port_remote = 5700;
- plink->u.osmotrx.clock_advance = 20;
- plink->u.osmotrx.rts_advance = 5;
+ plink->u.osmotrx.clock_advance = 2;
+ plink->u.osmotrx.rts_advance = 3;
/* attempt use newest TRXD version by default: */
plink->u.osmotrx.trxd_hdr_ver_max = TRX_DATA_FORMAT_VER;
}
--
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I7da3d0948f38e12342fb714b29f8edc5e9d0933d
Gerrit-Change-Number: 17766
Gerrit-PatchSet: 5
Gerrit-Owner: daniel <[email protected]>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: daniel <[email protected]>
Gerrit-Reviewer: dexter <[email protected]>
Gerrit-Reviewer: fixeria <[email protected]>
Gerrit-Reviewer: laforge <[email protected]>
Gerrit-Reviewer: neels <[email protected]>
Gerrit-Reviewer: pespin <[email protected]>
Gerrit-MessageType: merged
