Date: Thu, 30 Aug 2018 18:57:01 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Rajesh Kumar <rajfbsd@gmail.com> Cc: freebsd-usb@freebsd.org Subject: Re: Is FreeBSD-current XHCI 1.1 compliant? Message-ID: <a340e34c-68fc-f73d-57bd-336ec33cc1e8@selasky.org> In-Reply-To: <CAAO%2BANMuMsAKTsakMZc0dGD6ti%2B841dfhuVT=8Ni-%2BaYh_2FoA@mail.gmail.com> References: <CAAO%2BANMszVRzifqja_U=VPTvr%2BoOLXduBV4JyACJgBWv5p9cOQ@mail.gmail.com> <679a5fd9-a3ee-b4a6-8a0c-6a1a7b850154@selasky.org> <CAAO%2BANNfXodbjzT3YT-M-S9YE=%2BPrMy5ErTrOq=x5Hy9-jyWpA@mail.gmail.com> <7683a29a-2323-69ec-8f98-094980de62e7@selasky.org> <CAAO%2BANOSQ-F_Cat4AH59M8gtw-crdLunLYGv%2BbM%2BjgChAe1NEA@mail.gmail.com> <CAAO%2BANNFTVWpUGBtn%2BoW2Y3Ccv7QUAERea4onq%2BwopOxh-0vig@mail.gmail.com> <c5ace119-03fc-5a39-57ef-e3d1e4470dcc@selasky.org> <CAAO%2BANMuMsAKTsakMZc0dGD6ti%2B841dfhuVT=8Ni-%2BaYh_2FoA@mail.gmail.com>
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On 8/30/18 3:55 PM, Rajesh Kumar wrote: > So, does using streams mode helps in improving the storage performance with > USB? If so, what is needed to use streams mode effectively? Do we need to > consider anything else when taking USB performance numbers in FreeBSD? Hi, Streams mode might help with latency, that you can queue more transfers at the same time. Also streams mode used to be controversial, that not all hardware manufacturers supported it. USB is no replacement for a PCI hardware device or a SATA controller. The block size effectively decides the performance of your device. The USB XHCI controller has a configurable IRQ limit of 16000 IRQ/s. At this rate you can queue at most 4000-8000 SCSI jobs per second towards the USB SCSI implementation. If you use small block size, performance drops. If you use bigger block size, performance increase. In /usr/src/tools you'll find a small utility that benchmark USB storage devices, called usbtest. Beware it can brick your USB disk. --HPS
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