netdev - Re: [PATCH net-next v7 0/5] bpf: add two helpers to read perf event enabled/running time

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] [day] [month] [year] [list]

Message-Id: <20171007.230615.453122717434468471.davem@davemloft.net>
Date:   Sat, 07 Oct 2017 23:06:15 +0100 (WEST)
From:   David Miller <davem@...emloft.net>
To:     yhs@...com
Cc:     peterz@...radead.org, rostedt@...dmis.org, ast@...com,
        daniel@...earbox.net, netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH net-next v7 0/5] bpf: add two helpers to read perf
 event enabled/running time

From: Yonghong Song <yhs@...com>
Date: Thu, 5 Oct 2017 09:19:18 -0700

> Hardware pmu counters are limited resources. When there are more
> pmu based perf events opened than available counters, kernel will
> multiplex these events so each event gets certain percentage
> (but not 100%) of the pmu time. In case that multiplexing happens,
> the number of samples or counter value will not reflect the
> case compared to no multiplexing. This makes comparison between
> different runs difficult.
> 
> Typically, the number of samples or counter value should be
> normalized before comparing to other experiments. The typical
> normalization is done like:
>   normalized_num_samples = num_samples * time_enabled / time_running
>   normalized_counter_value = counter_value * time_enabled / time_running
> where time_enabled is the time enabled for event and time_running is
> the time running for event since last normalization.
> 
> This patch set implements two helper functions.
> The helper bpf_perf_event_read_value reads counter/time_enabled/time_running
> for perf event array map. The helper bpf_perf_prog_read_value read
> counter/time_enabled/time_running for bpf prog with type BPF_PROG_TYPE_PERF_EVENT.

Series applied to net-next, thanks.