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Differential D41059

tcp: improve layout of struct tcpcb
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Authored by tuexen on Jul 17 2023, 6:45 PM.
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imp
jhb
rrs
rscheff
cc
jtl
glebius
gallatin
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transport
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rGe4a873bf10b7: tcp: improve layout of struct tcpcb
Summary

Move the conditional stuff to the end. I hope we can remove TCPPCAP in FreeBSD 15.

Not using #ifdef for TCP_ACCOUNTING and TCP_REQUEST_TRK would increase the size of the struct. I am open to it, but based on a discussion with rrs@, the compromise was to move them to the end.

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tuexen created this revision.Jul 17 2023, 6:45 PM
Herald added a reviewer: transport. · View Herald TranscriptJul 17 2023, 6:45 PM
Herald added a subscriber: melifaro. · View Herald Transcript
tuexen requested review of this revision.Jul 17 2023, 6:45 PM
tuexen added a reviewer: gallatin.
tuexen edited the summary of this revision. (Show Details)Jul 17 2023, 6:47 PM
jhb added a comment.Jul 17 2023, 6:53 PM

Moving to the end is certainly sensible. Have you checked for any padding holes on at least LP64 with ptype /o in GDB?

emaste added a subscriber: emaste.Jul 17 2023, 7:49 PM
gallatin added inline comments.Jul 17 2023, 7:52 PM
sys/netinet/tcp_var.h
473

You're creating a 7 byte alignment hole.. I'd try to keep the uint8_t's together. Eg, put TCP_ACCOUNTING in a different place, and put the tcp_hybrid* after tcp_sendfile_track.

tuexen added inline comments.Jul 17 2023, 8:39 PM
sys/netinet/tcp_var.h
473

When moving TCP_ACCOUNTING around, it is not at the end anymore... That is the only intention here...

tuexen updated this revision to Diff 124788.Jul 17 2023, 9:48 PM

Avoid holes on 64-bit systems when all options are defined.

tuexen added inline comments.Jul 17 2023, 9:49 PM
sys/netinet/tcp_var.h
473

Moved things around, now avoiding any holes on 64-bit platforms when TCP_ACCOUNTING and TCP_REQUEST_TRK is defined.

gallatin accepted this revision.Jul 17 2023, 10:53 PM
imp accepted this revision.Jul 18 2023, 6:01 AM

I think this will work much better. Thanks

cc accepted this revision as: cc.Jul 18 2023, 2:17 PM
glebius accepted this revision.Jul 18 2023, 3:37 PM

About t_osd. It seems to be used only by alternative cc modules. Can we move it into their software context structures?

This revision was not accepted when it landed; it landed in state Needs Review.Jul 19 2023, 12:51 PM
Closed by commit rGe4a873bf10b7: tcp: improve layout of struct tcpcb (authored by tuexen). · Explain Why
This revision was automatically updated to reflect the committed changes.
tuexen added a commit: rGe4a873bf10b7: tcp: improve layout of struct tcpcb.

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sys/
netinet/
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Diff 124841

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sys/netinet/tcp_var.h

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