From owner-freebsd-hackers Tue Aug 7 12:19: 8 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from earth.backplane.com (earth-nat-cw.backplane.com [208.161.114.67]) by hub.freebsd.org (Postfix) with ESMTP id 9E84137B401; Tue, 7 Aug 2001 12:19:02 -0700 (PDT) (envelope-from dillon@earth.backplane.com) Received: (from dillon@localhost) by earth.backplane.com (8.11.4/8.11.2) id f77JJ1d35789; Tue, 7 Aug 2001 12:19:01 -0700 (PDT) (envelope-from dillon) Date: Tue, 7 Aug 2001 12:19:01 -0700 (PDT) From: Matt Dillon Message-Id: <200108071919.f77JJ1d35789@earth.backplane.com> To: Terry Lambert Cc: Mike Smith , Zhihui Zhang , freebsd-hackers@freebsd.org Subject: Re: Allocate a page at interrupt time References: <200108070739.f777dmi08218@mass.dis.org> <3B6FB0AE.8D40EF5D@mindspring.com> <200108071655.f77Gt9M32808@earth.backplane.com> <3B703029.2BB6D25A@mindspring.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG : :Matt Dillon wrote: :> :What "this", exactly? :> : :> :That "virtual wire" mode is actually a bad idea for some :> :applications -- specifically, high speed networking with :> :multiple gigabit ethernet cards? :> :> All the cpu's don't get the interrupt, only one does. : :I think that you will end up taking an IPI (Inter Processor :Interrupt) to shoot down the cache line during an invalidate :cycle, when moving an interrupt processing thread from one :CPU to another. For multiple high speed interfaces (disk or :network; doesn't matter), you will end up burining a *lot* :of time, without a lockdown. Cache line invalidation does not require an IPI. TLB shootdowns require IPIs. TLB shootdowns are unrelated to interrupt threads, they only occur when shared mmu mappings change. Cache line invalidation can waste cpu cycles -- when cache mastership changes occur between cpus due to threads being switched between cpus. I consider this a serious problem in -current. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message