linux-kernel - Re: [PATCH] perf_events: fix and improve x86 event scheduling

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]

Date:	Mon, 07 Nov 2011 15:56:10 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, robert.richter@....com,
	mingo@...e.hu, ming.m.lin@...el.com, ak@...ux.intel.com
Subject: Re: [PATCH] perf_events: fix and improve x86 event scheduling

On Mon, 2011-11-07 at 13:52 +0000, Stephane Eranian wrote:
> But given we limit the number of events to that of counters,
> we do have O(c^3). 

Right, but SNB without HT gives you 8 GP counters, yielding a rather big
number. Suppose you're trying to fill it with 9 cycle events (1 for the
fixed purpose thingy), that'll end up being: 9^3 = 729 = big number.

(arguably adding 9 cycle counters is a tad retarded, but hey ;-)

It would be good to try and get it down to somewhere near 81 again,
although my brain isn't currently providing any sane ideas on how.

> As for the map_idx, it's there to track the position of each event in the
> initial event list. We shuffle events between constrained and unconstrained.
> By stashing the map_idx in the hw_perf_event struct we avoid having to
> pass around yet another array.

Yeah, I saw why you needed it..
--
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/