linux-kernel - Re: [PATCH] perf session: Add option to copy events when queueing

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: <5237D710.2020301@gmail.com>
Date:	Mon, 16 Sep 2013 22:14:08 -0600
From:	David Ahern <dsahern@...il.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	acme@...stprotocols.net, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf session: Add option to copy events when queueing

On 9/16/13 10:40 AM, Frederic Weisbecker wrote:
>> Yes. I could make it the default behavior; just overhead in doing
>> that (malloc/copy for each event).
>
> Are there any tool that don't suffer from this bug somehow? If not then it must
> be applied unconditionally.

I believe only 'live' commands would be affected: top, kvm stat live, my 
local scheduling daemon. perf-trace bypasses session and time ordering 
(though I question that decision).

---8<---

>> size of event is determined by mmap_event (mmap2_event in latest
>> code) which is > 4096 because of the filename argument. Including
>> the event directly in sample_queue would balloon memory usage
>> (learned this the hard way!).
>
> Ah then perhaps we can allocate with the dynamic size of the event?

Yes, that's how I have it my patch -- allocate memory based on header 
size and copy in the queue_event function. I think we agree on this part 
now.

---8<---

>>> Although the mirrored os->sample_buffer condition check is a bit ugly and should move to
>>> a function. But the idea is there.
>>
>> Ok. That should be a separate patch. Are you going to submit that one?
>
> Yeah, unless you beat me at it :)

That's not going to happen on my end due to a recent time constraint 
(jury duty - minimum 1 week trial). At best I can do a patch in early 
October.

David

--
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/