linux-kernel - Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid option

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f24e38b0-3000-1306-7058-cc440557e733@gmail.com>
Date:   Fri, 31 Jul 2020 10:35:54 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Geneviève Bastien <gbastien@...satic.net>,
        Wang Nan <wangnan0@...wei.com>,
        Jeremie Galarneau <jgalar@...icios.com>
Subject: Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid
 option

On 7/31/20 10:15 AM, Jiri Olsa wrote:
>> It might also want to be implemented in a loop and iteration with minimal
>> time delta is chosen to improve synchronization accuracy and also mitigate
>> possible context switches between gettimeofday() and clock_gettime() calls.
> right, we could make this more accurate.. I'll post some follow up
> change with that

If it is handled through vdso (e.g., x86) both calls should be very fast
with no context switches and the margin of error is well less than the
usec resolution in the output.