forked from Minki/linux
dc14ca4644
sample_summary_print() uses accumulated period to calculate and display
per-sec averages. This period gets incremented by sampling interval each
time a new sample is formed, and thus equals to the number of samples
collected multiplied by this interval.
However, the totals are being calculated differently, they receive current
sample statistics already divided by the interval gotten as a difference
between sample timestamps for better precision -- in other words, they are
being incremented by the per-sec values each sample.
This leads to the excessive division of summary per-secs when interval != 1
sec. It is obvious pps couldn't become two times lower just from picking a
different sampling interval value:
$ samples/bpf/xdp_redirect_cpu -p xdp_prognum_n1_inverse_qnum -c all
-s -d 6 -i 1
< snip >
Packets received : 2,197,230,321
Average packets/s : 22,887,816
Packets redirected : 2,197,230,472
Average redir/s : 22,887,817
$ samples/bpf/xdp_redirect_cpu -p xdp_prognum_n1_inverse_qnum -c all
-s -d 6 -i 2
< snip >
Packets received : 159,566,498
Average packets/s : 11,397,607
Packets redirected : 159,566,995
Average redir/s : 11,397,642
This can be easily fixed by treating the divisor not as a period, but rather
as a total number of samples, and thus incrementing it by 1 instead of
interval. As a nice side effect, we can now remove so-named argument from a
couple of functions. Let us also create an "alias" for sample_output::rx_cnt::pps
named 'num' using a union since this field is used to store this number (period
previously) as well, and the resulting counter-intuitive code might've been a
reason for this bug.
Fixes:
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|---|---|---|
| .. | ||
| acrn | ||
| auxdisplay | ||
| binderfs | ||
| bpf | ||
| configfs | ||
| connector | ||
| fanotify | ||
| ftrace | ||
| hidraw | ||
| hw_breakpoint | ||
| kdb | ||
| kfifo | ||
| kmemleak | ||
| kobject | ||
| kprobes | ||
| landlock | ||
| livepatch | ||
| mei | ||
| nitro_enclaves | ||
| pidfd | ||
| pktgen | ||
| qmi | ||
| rpmsg | ||
| seccomp | ||
| timers | ||
| trace_events | ||
| trace_printk | ||
| uhid | ||
| v4l | ||
| vfio-mdev | ||
| vfs | ||
| watch_queue | ||
| watchdog | ||
| Kconfig | ||
| Makefile | ||