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
| ||
|
Date: Sat, 18 Jul 2009 23:00:55 -0400 From: Chris Snook <chris.snook@...il.com> To: john stultz <johnstul@...ibm.com> Cc: lkml <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...x.de>, Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...e.de>, nikolag@...ibm.com, Darren Hart <dvhltc@...ibm.com> Subject: Re: [RFC][PATCH] Introduce CLOCK_REALTIME_COARSE On Fri, Jul 17, 2009 at 7:39 PM, john stultz<johnstul@...ibm.com> wrote: > - if (likely(gtod->sysctl_enabled && gtod->clock.vread)) > + if (likely(gtod->sysctl_enabled)) This irks me. If the sysctl is enabled and the codepath is getting used often enough that we care about performance, branch prediction should do the right thing without compiler hints. On the other hand, if the sysctl is disabled, and the compiler is telling the cpu to ignore its branch predictor, it'll hurt. I don't think we should be wrapping (un)likely annotations around configuration options, unless we're biasing against debug conditions where we definitely don't care about performance. The patch is certainly no worse than the existing code, but while we have the hood up, it might be nice to remove the annotation, unless we're sure that it does no harm, and does some good. -- Chris -- 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/
Powered by blists - more mailing lists