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Differential D24657

update cwnd in both convex and concave regions like comment stated.
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Authored by rscheff on May 1 2020, 9:05 PM.
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tuexen
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transport
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rS364378: MFC r363397: Fix style and comment around concave/convex regions in TCP cubic.
rS363397: Fix style and comment around concave/convex regions in TCP cubic.
Summary

The current cubic code has an oversight that it missed updating cwnd
in the convex region. However, the comment in the code states, that
cwnd should be updated similarly in both convex and concave regions.

This has been reported by Vidhi Goel in Bug Report 238478.

Test Plan

Track the evolution of cwnd throuhg tcp friendly, concave
and convex regions and verify the behavior matches what RFC8312
(TCP Cubic) prescribes.

Diff Detail

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Build Status
Buildable 31888
Build 29442: arc lint + arc unit

Event Timeline

rscheff created this revision.May 1 2020, 9:05 PM
Herald added a subscriber: melifaro. · View Herald TranscriptMay 1 2020, 9:05 PM
rscheff requested review of this revision.May 1 2020, 9:05 PM
Harbormaster completed remote builds in B30852: Diff 71254.May 1 2020, 9:05 PM
rgrimes accepted this revision.Jun 23 2020, 5:03 AM

So, is FreeBSD getting close to a proper Cubic yet?

sys/netinet/cc/cc_cubic.c
188

I am only going to "NOTE" a style 9 issue here, I do not expect it fixed, as it was an existing issue, and it may be the whole file is this way, but we usually write "} else {" or "} else if {" and I am not sure why these extra new lines are here.

This revision is now accepted and ready to land.Jun 23 2020, 5:03 AM
Herald added a reviewer: transport. · View Herald TranscriptJun 23 2020, 5:03 AM
This revision now requires review to proceed.Jun 23 2020, 5:03 AM
rscheff updated this revision to Diff 73500.Jun 23 2020, 8:28 AM
  • style fix
Harbormaster completed remote builds in B31888: Diff 73500.Jun 23 2020, 8:28 AM
rgrimes accepted this revision.Jun 23 2020, 2:05 PM
rscheff added a comment.Jul 21 2020, 10:38 AM

Re-inspecting the suggested fix. The concave region is where cubic_wnd < cwnd_max, and the convex region is cubic_cwnd > cwnd_max.

However, this if bracket is only preventing snd_cwnd from shrinking.

Will adjust the style and make a comment.

rscheff updated this revision to Diff 74734.Jul 21 2020, 10:51 AM
  • only update style and comment. logic was ok before.
Harbormaster completed remote builds in B32452: Diff 74734.Jul 21 2020, 10:51 AM
tuexen accepted this revision.Jul 21 2020, 12:47 PM
This revision is now accepted and ready to land.Jul 21 2020, 12:47 PM
rgrimes accepted this revision.Jul 21 2020, 3:19 PM
Closed by commit rS363397: Fix style and comment around concave/convex regions in TCP cubic. (authored by rscheff). · Explain WhyJul 21 2020, 4:22 PM
This revision was automatically updated to reflect the committed changes.
rscheff added a commit: rS363397: Fix style and comment around concave/convex regions in TCP cubic..
Herald added a subscriber: imp. · View Herald TranscriptJul 21 2020, 4:22 PM
rscheff added a commit: rS364378: MFC r363397: Fix style and comment around concave/convex regions in TCP cubic..Aug 19 2020, 10:40 AM

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sys/
netinet/
cc/
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Diff 73500

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sys/netinet/cc/cc_cubic.c

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