linux-kernel - Re: [PATCH v7] NVMe: conversion to blk-mq

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Message-ID: <CAOu_J6kocZZ1mRQeSidyqJ_Ew0F_POS30v2kgUZX2wDOOnuExg@mail.gmail.com>
Date:	Thu, 12 Jun 2014 00:22:57 +0200
From:	Matias Bjørling <m@...rling.me>
To:	Matthew Wilcox <willy@...ux.intel.com>
Cc:	Jens Axboe <axboe@...com>, Keith Busch <keith.busch@...el.com>,
	"sbradshaw@...ron.com" <sbradshaw@...ron.com>,
	"tom.leiming@...il.com" <tom.leiming@...il.com>,
	"hch@...radead.org" <hch@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH v7] NVMe: conversion to blk-mq

On Wed, Jun 11, 2014 at 7:09 PM, Matthew Wilcox <willy@...ux.intel.com> wrote:
> On Wed, Jun 11, 2014 at 10:54:52AM -0600, Jens Axboe wrote:
>> OK, so essentially any single request must be a virtually contig piece
>> of memory. Is there any size limitations to how big this contig segment
>> can be?
>
> The maximum size of an I/O is 65536 sectors.  So on a 512-byte sector
> device, that's 32MB, but on a 4k sector size device, that's 128MB.
>
>> I think this is unique requirement, at least I haven't seen other pieces
>> of hardware have it. But it would be pretty trivial to add a setting to
>> limit merges based on virtually contig, similarly to what is done for
>> number of physical segments.
>
> I think there might be an FCoE device with that requirement too.

I've rebased nvmemq_review and added two patches from Jens that add
support for requests with single range virtual addresses.

Keith, will you take it for a spin and see if it fixes 068 for you?

There might still be a problem with some flushes, I'm looking into this.
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