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Message-ID: <20081218134006.GP32491@kernel.dk> Date: Thu, 18 Dec 2008 14:40:06 +0100 From: Jens Axboe <jens.axboe@...cle.com> To: Vladislav Bolkhovitin <vst@...b.net> Cc: Fabio Checconi <fabio@...dalf.sssup.it>, linux-kernel@...r.kernel.org Subject: Re: Dynamic switching of io_context On Wed, Dec 17 2008, Vladislav Bolkhovitin wrote: > >I haven't seen the rest of the code, so I may be wrong, but I suppose > >that a better approach would be to use CLONE_IO to share io contexts, > >if possible. > > Unfortunately, it would be very non-optimal. As it is known, to achieve > the best performance with async. IO, it should be submitted by a limited > number of threads <= CPU count. So, the only way to submit IO from each > of, e.g. 100, clients in a dedicated per-client IO context is to > dynamically switch io_context of the current threads to io_context of > the client before IO submission. There's also likely to be another use of exactly the same type of thing - the acall patches from Zach. At least my vision of the punt-to-thread approach would be very similar: grab an available thread and attach it to a given IO context. So while I did mention exactly what Fabio outlines in my initial mail on this, a generic way to attach/detach IO contexts from processes/threads would be useful outside of this project. nfsd comes to mind as well. -- Jens Axboe -- 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/
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