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 PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 6 Mar 2014 23:41:46 +0100 From: Andi Kleen <andi@...stfloor.org> To: Peter Zijlstra <peterz@...radead.org> Cc: Kevin Easton <kevin@...rana.org>, Andi Kleen <andi@...stfloor.org>, Thomas Gleixner <tglx@...utronix.de>, Khalid Aziz <khalid.aziz@...cle.com>, One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>, akpm@...ux-foundation.org, viro@...iv.linux.org.uk, oleg@...hat.com, linux-kernel@...r.kernel.org Subject: Re: [RFC] [PATCH] Pre-emption control for userspace On Thu, Mar 06, 2014 at 02:59:46PM +0100, Peter Zijlstra wrote: > On Thu, Mar 06, 2014 at 11:13:33PM +1100, Kevin Easton wrote: > > On Tue, Mar 04, 2014 at 04:51:15PM -0800, Andi Kleen wrote: > > > Anything else? > > > > If it was possible to make the time remaining in the current timeslice > > available to userspace through the vdso, the thread could do something like: > > Assuming we can do per-cpu values in the VDSO; this would mean hitting > that cacheline on every context switch and wakeup. That's a complete > non-starter performance wise. If you worry about fetching it you can always prefetch it early. > > if (sys_timeleft() < CRITICAL_SECTION_SIZE) > > yield(); > > lock(); > > > > to avoid running out of timeslice in the middle of the critical section. > > Can still happen, the effective slice of a single runnable task is > infinite, the moment another task gets woken this gets reduced to a finite > amount, we then keep reducing the slice until there are about 8 runnable > tasks (assuming you've not poked at any sysctls). I guess it could be some predicted value, similar to how the menu governour works. -Andi -- ak@...ux.intel.com -- Speaking for myself only. -- 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