linux-kernel - Re: [patch] x86: unify/rewrite SMP TSC sync code

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Mon, 27 Nov 2006 10:41:20 -0800
From:	Max Krasnyansky <maxk@...lcomm.com>
To:	Robert Crocombe <rcrocomb@...il.com>
CC:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86: unify/rewrite SMP TSC sync code

> Using gtod() can amount to a substantial disturbance of the thing to
> be measured.  Using rdtsc, things seem reliable so far, and we have an
> FPGA (accessed through the PCI bus) that has been programmed to give
> access to an 8MHz clock and we do some checks against that.

Same here. gettimeofday() is way too slow (dual Opteron box) for the
frequency I need to call it at. HPET is not available. But TSC is doing just
fine. Plus in my case I don't care about sync between CPUs (thread that uses
TSC is running on the isolated CPU) and I have external time source that takes
care of the drift.

So please no trapping of the RDTSC. Making it clear (bold kernel message during
boot :-) that TSC(s) are not in sync or unstable (from GTOD point of view) is of
course perfectly fine.

Thanx
Max
-
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/