Date: Fri, 30 Jan 2015 10:38:03 -0700 From: Scott Long <scott4long@yahoo.com> To: Sibananda Sahu <sibananda.sahu@avagotech.com> Cc: freebsd-scsi@freebsd.org Subject: Re: How to send 1MB I/O size in a single I/O request without split Message-ID: <F29BEC27-98DB-4588-A5A3-5AF19DAF5FF8@yahoo.com> In-Reply-To: <37dd5147bdbf0ea417d2fdfb31565358@mail.gmail.com> References: <f94a31843fde43237d9aa13bbe543ddf@mail.gmail.com> <8B56B74C-7EBC-4D1B-89AB-46DA8ED05DD5@yahoo.com> <923e4c2e65d29f2f39e0aa2f6d4ab38a@mail.gmail.com> <37dd5147bdbf0ea417d2fdfb31565358@mail.gmail.com>
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> On Jan 30, 2015, at 3:18 AM, Sibananda Sahu = <sibananda.sahu@avagotech.com> wrote: >=20 > Hi Scott, >=20 > One more thing to ask. >=20 > I think even if I will modify the bus_dma_tag in our driver to have a = max > segment of 4K, the max I/O length per I/O request that will come is = 128KB > because of the MAXPHYS limitation. > I have tested this by restricting the MAXPHYS to 128KB again and when = I > requested an I/O with bs=3D1M the I/O was split with various length = I/O > requests. >=20 > Does this implies that tuning the MAXPHYS is the ultimate solution to = get > larger I/O size?? Yes. You will need to rebuild your kernel with the larger size. Some = day we might default to a larger size, or make it dynamic. Scott
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