linux-kernel - Re: AMD X2 unsynced TSC fix?

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: <20061028193217.GD1709@1wt.eu>
Date:	Sat, 28 Oct 2006 21:32:18 +0200
From:	Willy Tarreau <w@....eu>
To:	thockin@...kin.org
Cc:	Andi Kleen <ak@...e.de>, Lee Revell <rlrevell@...-job.com>,
	Luca Tettamanti <kronos.it@...il.com>,
	linux-kernel@...r.kernel.org, john stultz <johnstul@...ibm.com>
Subject: Re: AMD X2 unsynced TSC fix?

On Sat, Oct 28, 2006 at 12:18:00PM -0700, thockin@...kin.org wrote:
> On Sat, Oct 28, 2006 at 09:15:15PM +0200, Willy Tarreau wrote:
> > > While gtod is time critical and often appears high on profile lists it is 
> > > normally not as time critical as you're claiming it is; especially not
> > > time critical enough to warrant such radical action.
> > 
> > Yes it was, because the small gain of using a dual core with such
> > a workload was clearly lost by that change. IIRC, I reached 25000
> > sessions/s on dual core with TSC if I didn't care about the clock,
> > 20000 without TSC, and 18000 on single core+TSC. But with the sniffer,
> > it was even worse : I had 500 kpps in dual-core+TSC, 70kpps without
> > TSC and 300 kpps with single-core+TSC. Since I had to buy the same
> > machines for both uses, this last argument was enough for me to stick
> > to a single core.
> 
> Was the problem that they were not synced at poweron or that they would
> drift due to power-states?

They resynced at power up, but would constantly drift. I don't even know
if it was caused by power states. When the machine was loaded, a single
task moving across the cores could see its time jump back and forth 
several times a second by an offset sometimes close to +2/-2s.

> Did you try running with idle=poll, to avoid ever entering C1 state (hlt)?

Yes, I remember trying such things. I also tried 'nohlt', completely
disabling power management, including ACPI, etc... I also tried vanilla
kernels as well as severely patched ones, but the problem remained the
same in all circumstances, that only 'notsc' could solve.

BTW, I've just found a remain of dmesg capture after boot in case you'd
like to look for anything in it.

Regards,
Willy

-
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/