m_uiotombuf: write total memory length of the allocated chain in pkthdr
ClosedPublic
Actions

Authored by glebius on May 23 2022, 9:02 PM.

Details

Reviewers

Group Reviewers

network
transport

Commits

rG9b841b0e2390: m_uiotombuf: write total memory length of the allocated chain in pkthdr

Summary

Data allocated by m_uiotombuf() usually goes into a socket buffer.
We are interested in the length of useful data to be added to sb_ccc,
as well as total memory used by mbufs. The later would be added to
sb_mbcnt. Calculating this value at allocation time allows to save
on extra traversal of the mbuf chain.

Diff Detail

Repository

rS FreeBSD src repository - subversion

Lint

Lint Passed

Unit

No Test Coverage

Build Status

Buildable 45682
Build 42570: arc lint + arc unit

Event Timeline

glebius created this revision.May 23 2022, 9:02 PM

Herald added a subscriber: imp. · View Herald TranscriptMay 23 2022, 9:02 PM

glebius requested review of this revision.May 23 2022, 9:02 PM

Harbormaster completed remote builds in B45682: Diff 106300.May 23 2022, 9:02 PM

glebius added a parent revision: D35300: unix/dgram: use minimal possible socket buffer for PF_UNIX/SOCK_DGRAM.May 23 2022, 9:02 PM

glebius added a child revision: D35302: unix/dgram: reduce mbuf chain traversals in send(2) and recv(2).

glebius added a child revision: D35305: libc/syslog: deprecate use of "/var/run/logpriv".May 23 2022, 9:07 PM

glebius added reviewers: network, markj.May 23 2022, 9:13 PM

markj added inline comments.May 24 2022, 3:22 PM

sys/sys/mbuf.h
209	How is a consumer supposed to know whether `memlen` is populated or not? It sounds very general but it's only set by m_uiotombuf(). How do we know that setting `memlen` won't clobber a field in PH_loc? I'm not very familiar with PH_loc's usage so it's not clear to me.

glebius added inline comments.May 25 2022, 7:39 AM

sys/sys/mbuf.h
209	At this moment m_uiotombuf() supports it, but other chain allocation functions can and should support it future. The PH_loc belongs to a subsystem that is sure it owns the mbuf. For a freshly allocated mbuf this works perfect.