Re: [PATCH 0/2] tools: Skip backward time entries


Brendan Gregg
 

I'm ok with the workaround code, but I'd like a comment that clearly explains it for future maintainers and copy-n-pasters. Eg:

// Skip entries with backwards time: temp workaround for #728

Then people know it's a temp workaround, and they can lookup https://github.com/iovisor/bcc/issues/728

Brendan

On Tue, Aug 28, 2018 at 9:05 PM, Y Song <ys114321@...> wrote:
Jiri,

The change looks good. Could you generate a pull request against the
bcc/iovisor github repository?

Thanks!

Yonghong
On Tue, Aug 28, 2018 at 5:01 AM Jiri Olsa <jolsa@...> wrote:
>
> hi,
> on RHEL7 we are facing timing issues in some bcc-tools
> scripts. The time subsystem might return backward timestamp
> via bpf_ktime_get_ns and thus screw up latency computation.
>
> This seems to be RHEL7 kernel issue and needs to be fixed,
> however meanwhile it'd be nice if affected scripts display
> sane values despite the kernel issue.
>
> This patchset harden 2 scripts (xfsslower and ext4dist)
> we saw this behaviour so far, to ensure the latency is
> always > 0.
>
> thanks,
> jirka
>
>
> ---
> Jiri Olsa (2):
>       tools: Skip backward time entries in xfsslower
>       tools: Skip backward time entries in ext4dist
>
>  tools/ext4dist.py  | 10 ++++++++--
>  tools/xfsslower.py |  9 ++++++++-
>  2 files changed, 16 insertions(+), 3 deletions(-)
>
>
>

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