Re: [PATCH v4 00/11] simplify block layer based on immutable biovecs

From: Ming Lin <mlin@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Jens Axboe <axboe@kernel.dk>, Dongsu Park <dpark@posteo.net>
Subject: Re: [PATCH v4 00/11] simplify block layer based on immutable biovecs
Date: Thu, 28 May 2015 23:39:52 -0700	[thread overview]
Message-ID: <CAF1ivSYt1bD=Uy0s+9m9WvbuKy7c9wFWvvAJ3s3CPs7h8XcjUw@mail.gmail.com> (raw)
In-Reply-To: <20150525135121.GB25855@lst.de>

On Mon, May 25, 2015 at 6:51 AM, Christoph Hellwig <hch@lst.de> wrote:
> On Sun, May 24, 2015 at 12:37:32AM -0700, Ming Lin wrote:
>> > Except for that these changes looks good, and the previous version
>> > passed my tests fine, so with some benchmarks you'ĺl have my ACK.
>>
>> I'll test it on a 2 sockets server with 10 NVMe drives on Monday.
>> I'm going to run fio tests:
>> 1. raw NVMe drives direct IO read/write
>> 2. ext4 read/write
>>
>> Let me know if you have other tests that I can run.
>
> That sounds like a good start, but the most important tests would be
> those that will cause a lot of splits with the new code.
>
> E.g. some old ATA devices using the piix driver, some crappy USB
> device that just allows 64 sector transfers.  Or maybe it's better
> to just simulate the case by dropping max_sectors to ease some pain :)

That 2 sockets server has been busy running other things.

I did a quick test with 1 NVMe drive to simulate 64 sector transfers.
echo 32 > /sys/block/nvme0n1/queue/max_sectors_kb

Then run fio 1M block size read that should cause a lot of splits.
As expected, no obvious difference with and without the patches.

I'll run more tests once the server is free, probably next week.

Or would you think the performance data on a PC with 1 NVMe drive is OK?

>
> The other cases is DM/MD ѕtripes or RAID5/6 with small stripe sizes.

Will also run MD stripes test.