linux-kernel - Re: newidle balancing in NUMA domain?

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:	Tue, 24 Nov 2009 09:24:26 -0800
From:	Jason Garrett-Glaser <darkshikari@...il.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: newidle balancing in NUMA domain?

> Quite a few being one test case, and on a program with a horrible
> parallelism design (rapid heavy weight forks to distribute small
> units of work).

> If x264 is declared dainbramaged, that's fine with me too.

We did multiple benchmarks using a thread pool and it did not help.
If you want to declare our app "braindamaged", feel free, but pooling
threads to avoid re-creation gave no benefit whatsoever.  If you think
the parallelism methodology is wrong as a whole, you're basically
saying that Linux shouldn't be used for video compression, because
this is the exact same threading model used by almost every single
video encoder ever made.  There are actually a few that use
slice-based threading, but those are actually even worse from your
perspective, because slice-based threading spawns mulitple threads PER
FRAME instead of one per frame.

Because of the inter-frame dependencies in video coding it is
impossible to efficiently get a granularity of more than one thread
per frame.  Pooling threads doesn't change the fact that you are
conceptually creating a thread for each frame--it just eliminates the
pthread_create call.  In theory you could do one thread per group of
frames, but that is completely unrealistic for real-time encoding
(e.g. streaming), requires a catastrophically large amount of memory,
makes it impossible to track the bit buffer, and all other sorts of
bad stuff.

Jason Garrett-Glaser
--
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/