Date: Wed, 14 Jan 2015 16:23:12 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Ian Lepore <ian@freebsd.org> Cc: kott <kmatpral@yahoo.com>, freebsd-usb@freebsd.org Subject: Re: usb_pc_cpu_flush Message-ID: <54B689E0.7040005@selasky.org> In-Reply-To: <1421247832.14601.258.camel@freebsd.org> References: <1419359192795-5975583.post@n5.nabble.com> <5499E734.1070507@selasky.org> <1419392511197-5975691.post@n5.nabble.com> <549A811D.3060204@selasky.org> <1419416870924-5975752.post@n5.nabble.com> <1419423740820-5975763.post@n5.nabble.com> <549AB711.8070005@selasky.org> <1419431704871-5975773.post@n5.nabble.com> <549BF430.8000207@selasky.org> <1419877515606-5976832.post@n5.nabble.com> <1421133295061-5980199.post@n5.nabble.com> <1421160576.14601.175.camel@freebsd.org> <54B53956.4090708@selasky.org> <1421163656.14601.184.camel@freebsd.org> <54B54073.6000409@selasky.org> <1421166591.14601.195.camel@freebsd.org> <54B54D4D.3010805@selasky.org> <1421180700.14601.209.camel@freebsd.org> <54B5FAE8.7020705@selasky.org> <1421247832.14601.258.camel@freebsd.org>
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On 01/14/15 16:03, Ian Lepore wrote: > If you are allocating the memory using bus_dmamem_alloc() then no, > absolutely not. It's working for you by accident because of the > USB_HOST_ALIGN hacks which I think date back to freebsd 8 or so. > > When I talked to you a couple years ago about doing it the right way, > you were outraged (perhaps rightly so) about the inefficiency involved, > because of things like allocating a 16 byte buffer causing the > allocation of a full page just so that the caching attributes could be > changed. So I fixed that with the busdma zone allocator stuff that > makes it very efficient to allocate many tiny dma buffers (coherent or > not), and when you use buffers allocated that way, the sync operations > code can make some safe assumptions and avoid doing bounces due to > cacheline alignments. > > If buffers were allocated right-sized now that it's efficient to do so, > the USB_HOST_ALIGN hack could go away. Hmm, actually it might be > necessary to start using the busdma zone allocator in mips as well > before undoing the hack. Hi Ian, This sounds good. I'll make a quick patch you can try this week which splits the USB busdma allocations again. It is a quite trivial thing to do. Can you or Kott then test this patch? --HPS
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