linux-kernel - Re: [PATCH 0/4] pending scheduler updates

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: <20081022121007.GG8095@elte.hu>
Date:	Wed, 22 Oct 2008 14:10:07 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Galbraith <efault@....de>
Cc:	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] pending scheduler updates


* Mike Galbraith <efault@....de> wrote:

> On Wed, 2008-10-22 at 12:03 +0200, Mike Galbraith wrote:
> 
> > It has positive effects too, but IMHO, the bad outweigh the good.
> 
> BTW, most dramatic on the other end of the spectrum is pgsql+oltp.  
> With preemption as is, it collapses as load climbs to heavy with 
> preemption knobs at stock.  Postgres uses user-land spinlocks and 
> _appears_ to wake others while these are still held.  For this load, 
> there is such a thing as too much short-term fairness, preempting lock 
> holder creates nasty gaggle of contended lock spinners.  It's curable 
> with knobs, and I think it's postgres's own fault, but may be wrong.
> 
> With that patch, pgsql+oltp scales perfectly.

hm, tempting.

Have you tried to hack/fix pgsql to do proper wakeups?

Right now pgsql it punishes schedulers that preempt it while it is 
holding totally undeclared (to the kernel) user-space spinlocks ... 

Hence postgresql is rewarding a _bad_ scheduler policy in essence. And 
pgsql scalability seems to fall totally apart above 16 cpus - regardless 
of scheduler policy.

	Ingo
--
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/