linux-kernel - Re: [PATCH 0/6] perf core: Read from overwrite ring buffer

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: <20160120022020.GA89318@ast-mbp.thefacebook.com>
Date:	Tue, 19 Jan 2016 18:20:21 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>
Cc:	peterz@...radead.org, ast@...nel.org, linux-kernel@...r.kernel.org,
	He Kuang <hekuang@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>, pi3orama@....com
Subject: Re: [PATCH 0/6] perf core: Read from overwrite ring buffer

On Wed, Jan 20, 2016 at 09:37:42AM +0800, Wangnan (F) wrote:
> 
> 
> On 2016/1/20 1:42, Alexei Starovoitov wrote:
> >On Tue, Jan 19, 2016 at 11:16:44AM +0000, Wang Nan wrote:
> >>This patchset introduces two methods to support reading from overwrite.
> >>
> >>  1) Tailsize: write the size of an event at the end of it
> >>  2) Backward writing: write the ring buffer from the end of it to the
> >>     beginning.
> >what happend with your other idea of moving the whole header to the end?
> >That felt better than either of these options.
> 
> I'll try it today. However, putting all of the three together is
> not as easy as this patchset.

I'm missing something. Why all three in one set?
Since you have 1 and 2 implemented, benchmark them with absolute
numbers and then implement this last one without any prior baggage
and benchmark it as well. I think it should be the fastest
and the cleanest. We don't need ten different ways to do one thing.