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: Tue, 28 Oct 2014 11:03:53 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Will Deacon <will.deacon@....com> Cc: Peter Zijlstra <peterz@...radead.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Russell King - ARM Linux <linux@....linux.org.uk>, Benjamin Herrenschmidt <benh@...nel.crashing.org> Subject: Re: [RFC PATCH 1/2] zap_pte_range: update addr when forcing flush after TLB batching faiure On Tue, Oct 28, 2014 at 10:07 AM, Will Deacon <will.deacon@....com> wrote: > > I don't think that's necessarily true, at least not on the systems I'm > familiar with. A table walk can be comparatively expensive, particularly > when virtualisation is involved and the depth of the host and guest page > tables starts to grow -- we're talking >20 memory accesses per walk. By > contrast, the TLB invalidation messages are asynchronous and carried on > the interconnect (a DSB instruction is used to synchronise the updates). ">20 memory accesses per *walk*"? Isn't the ARM a regular table? So once you've gone down to the pte level, it's just an array, regardless of how many levels there are. But I guess there are no actual multi-socket ARM's around in real life, so you probably don't see the real scaling costs. Within a die, you're probably right that the overhead is negligible. Linus -- 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