linux-kernel - Re: [PATCH] perf_events: add sampling period randomization support (v2)

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: <20100304113212.GG21977@elte.hu>
Date:	Thu, 4 Mar 2010 12:32:12 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	eranian@...gle.com
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org,
	paulus@...ba.org, fweisbec@...il.com, perfmon2-devel@...ts.sf.net,
	robert.richter@....com, eranian@...il.com, davem@...emloft.net,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH] perf_events: add sampling period randomization support
 (v2)


* eranian@...gle.com <eranian@...gle.com> wrote:

> This patch adds support for randomizing the sampling period.  Randomization 
> is very useful to mitigate the bias that exists with sampling. The random 
> number generator does not need to be sophisticated. This patch uses the 
> builtin random32() generator.

> +	if (width > 63 || attr->freq)
> +		return -EINVAL;

Why not for freq counters? Those are semi-randomized already, but it might 
make sense to make them 'more' randomized in special circumstances. That would 
also allow us to enable the randomization in perf top and perf record, by 
default.

Without that we'd have no immediate usecase and no way to ensure that this 
code works as intended.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/