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b52ba22c70
The default ping-pong uses sizeof(int) (4 bytes) per iteration, which
exercises only the pipe-buffer merge path and keeps allocation entirely
out of the picture. That makes the bench a useful scheduler / context-
switch latency probe but unable to surface anything from the pipe
page-allocation hot path.
Add a -s/--write-size option that sets the bytes written and read per
ping-pong iteration. The buffer is allocated for each side via struct
thread_data and replaces the on-stack int previously used. The default
remains sizeof(int) so existing invocations are unchanged.
With --write-size set above PAGE_SIZE the bench drives anon_pipe_write()
through alloc_page() (or the bulk pre-alloc, if the relevant patch is
applied), which is what we want when measuring pipe locking and page
allocation work.
The bench is a ping-pong: both sides call write() before read(), so a
single write_size payload must fit entirely in the pipe buffer or both
sides deadlock waiting for the other to drain.
Resize the pipe via F_SETPIPE_SZ to match write_size (skipped at the
sizeof(int) default), and error out cleanly when the request exceeds
/proc/sys/fs/pipe-max-size.
Committer testing:
⬢ [acme@toolbx perf-tools-next]$ perf bench sched pipe
# Running 'sched/pipe' benchmark:
# Executed 1000000 pipe operations between two processes
Total time: 0.915 [sec]
0.915493 usecs/op
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| .. | ||
| bpf_skel | ||
| bench.h | ||
| breakpoint.c | ||
| Build | ||
| epoll-ctl.c | ||
| epoll-wait.c | ||
| evlist-open-close.c | ||
| find-bit-bench.c | ||
| futex-hash.c | ||
| futex-lock-pi.c | ||
| futex-requeue.c | ||
| futex-wake-parallel.c | ||
| futex-wake.c | ||
| futex.c | ||
| futex.h | ||
| inject-buildid.c | ||
| kallsyms-parse.c | ||
| mem-functions.c | ||
| mem-memcpy-arch.h | ||
| mem-memcpy-x86-64-asm-def.h | ||
| mem-memcpy-x86-64-asm.S | ||
| mem-memset-arch.h | ||
| mem-memset-x86-64-asm-def.h | ||
| mem-memset-x86-64-asm.S | ||
| numa.c | ||
| pmu-scan.c | ||
| sched-messaging.c | ||
| sched-pipe.c | ||
| sched-seccomp-notify.c | ||
| synthesize.c | ||
| syscall.c | ||
| uprobe.c | ||