Date: Tue, 22 Jan 2013 12:12:16 -0500 From: John Baldwin <jhb@freebsd.org> To: Adrian Chadd <adrian@freebsd.org> Cc: Barney Cordoba <barney_cordoba@yahoo.com>, Luigi Rizzo <rizzo@iet.unipi.it>, freebsd-net@freebsd.org Subject: Re: two problems in dev/e1000/if_lem.c::lem_handle_rxtx() Message-ID: <201301221212.16628.jhb@freebsd.org> In-Reply-To: <CAJ-Vmomd1ivZjWdiC8_O1qwim2dctq1o%2By5=UH2eivU4NdCOAQ@mail.gmail.com> References: <1358610450.75691.YahooMailClassic@web121604.mail.ne1.yahoo.com> <201301191114.29959.jhb@freebsd.org> <CAJ-Vmomd1ivZjWdiC8_O1qwim2dctq1o%2By5=UH2eivU4NdCOAQ@mail.gmail.com>
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On Saturday, January 19, 2013 8:19:19 pm Adrian Chadd wrote: > On 19 January 2013 08:14, John Baldwin <jhb@freebsd.org> wrote: > > > However, I did describe an alternate setup where you can fix this. Part of > > the key is to get various NICs to share a single logical queue of tasks. You > > could simulate this now by having all the deferred tasks share a single > > taskqueue with a pool of tasks, but that will still not fully cooperate with > > ithreads. To do that you have to get the interrupt handlers themselves into > > the shared taskqueue. Some changes I have in a p4 branch allow you to do that > > by letting interrupt handlers reschedule themselves (avoiding the need for a > > separate task and preventing the task from running concurrently with the > > interrupt handler) and providing some (but not yet all) of the framework to > > allow multiple devices to share a single work queue backed by a shared pool of > > threads. > > How would that work when I want to pin devices to specific cores? Note that the setup allows you to bind things however you want. By default it uses the current model (each IRQ uses a dedicated queue with a single thread). The idea is to provide the flexbility so that you can glue things together in whatever way makes the most sense. In a router that tends to get into livelock using a shared queue may make more sense. However, you are not forced to use that for other workloads where it does not. -- John Baldwin
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