CVS commit: src

["Andrew Doran" <ad%netbsd.org@localhost>]

Module Name:    src
Committed By:   ad
Date:           Fri Oct 13 19:07:09 UTC 2023

Modified Files:
        src/sys/ddb: db_command.c db_interface.h db_xxx.c
        src/sys/kern: sys_pipe.c
        src/sys/sys: pipe.h
        src/usr.bin/fstat: fstat.c

Log Message:
Simplify/streamline pipes a little bit:

- Allocate only one struct pipe not two (no need to be bidirectional here).
- Then use f_flag (FREAD/FWRITE) to figure out what to do in the fileops.
- Never wake the other side or acquire long-term (I/O) lock unless needed.
- Whenever possible, defer wakeups until after locks have been released.
- Do some things locklessly in pipe_ioctl() and pipe_poll().

Some notable results:

- -30% latency on a 486DX2/66 doing 1 byte ping-pong within a single process.
- 2.5x less lock contention during "make cleandir" of src on a 48 CPU machine.
- 1.5x bandwith with 1kB messages on the same 48 CPU machine (8kB: same b/w).


To generate a diff of this commit:
cvs rdiff -u -r1.186 -r1.187 src/sys/ddb/db_command.c
cvs rdiff -u -r1.41 -r1.42 src/sys/ddb/db_interface.h
cvs rdiff -u -r1.77 -r1.78 src/sys/ddb/db_xxx.c
cvs rdiff -u -r1.164 -r1.165 src/sys/kern/sys_pipe.c
cvs rdiff -u -r1.39 -r1.40 src/sys/sys/pipe.h
cvs rdiff -u -r1.118 -r1.119 src/usr.bin/fstat/fstat.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.