| 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
| ||
|
Message-ID: <Pine.LNX.4.64.0702140059390.727@home.oyster.ru> Date: Wed, 14 Feb 2007 01:01:26 +0300 (MSK) From: malc <av1474@...tv.ru> To: Pavel Machek <pavel@....cz> cc: Con Kolivas <kernel@...ivas.org>, linux-kernel@...r.kernel.org Subject: Re: CPU load On Mon, 12 Feb 2007, Pavel Machek wrote: > Hi! > >> The kernel looks at what is using cpu _only_ during the >> timer >> interrupt. Which means if your HZ is 1000 it looks at >> what is running >> at precisely the moment those 1000 timer ticks occur. It >> is >> theoretically possible using this measurement system to >> use >99% cpu >> and record 0 usage if you time your cpu usage properly. >> It gets even >> more inaccurate at lower HZ values for the same reason. > > I have (had?) code that 'exploits' this. I believe I could eat 90% of cpu > without being noticed. Slightly changed version of hog(around 3 lines in total changed) does that easily on 2.6.18.3 on PPC. http://www.boblycat.org/~malc/apc/load-hog-ppc.png -- vale - 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