linux-kernel - Re: [KVM-RFC PATCH 1/2] eventfd: add an explicit srcu based notifier interface

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: <alpine.DEB.1.10.0906181047040.32646@makko.or.mcafeemobile.com>
Date:	Thu, 18 Jun 2009 10:52:24 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
cc:	Gregory Haskins <ghaskins@...ell.com>, kvm@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	avi@...hat.com, paulmck@...ux.vnet.ibm.com,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [KVM-RFC PATCH 1/2] eventfd: add an explicit srcu based notifier
 interface

On Thu, 18 Jun 2009, Michael S. Tsirkin wrote:

> On Wed, Jun 17, 2009 at 04:21:19PM -0700, Davide Libenzi wrote:
> > The interface is just ugly IMO. You have eventfd_signal() that can sleep, 
> > or not, depending on the registered ->signal() function implementations.
> > This is pretty bad, a lot worse than the theoretical us spent in the 
> > schedule_work() processing.
> 
> I agree. How about the idea of introducing eventfd_signal_from_task
> which can sleep? Does this sound same?

You're basically asking to double the size of eventfd, make the signal 
path heavier, make the eventf size bigger, w/out having provided any *real 
life* measurement whatsoever to build a case for it.
WAY too much stuff went in by just branding the latest coolest names as 
reasons for them.
And all this to remove the wakeup of a *kernel* thread going to run in the 
same CPU where the work has been scheduled.
Come back with *replicable* real life benchmarks, and then we'll see what 
the best approach to address it will be.



- Davide


--
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/