linux-kernel - Re: [External] : Re: [bug-report] 5-9% FIO randomwrite ext4 perf regression on 6.12.y kernel

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Message-ID: <20241122121304.GA25877@lst.de>
Date: Fri, 22 Nov 2024 13:13:04 +0100
From: Christoph Hellwig <hch@....de>
To: Paul Webb <paul.x.webb@...cle.com>
Cc: Jens Axboe <axboe@...nel.dk>, Phil Auld <pauld@...hat.com>,
	Chaitanya Kulkarni <chaitanyak@...dia.com>,
	Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
	Ramanan Govindarajan <ramanan.govindarajan@...cle.com>,
	Sagi Grimberg <sagi@...mberg.me>, Christoph Hellwig <hch@....de>,
	Keith Busch <kbusch@...nel.org>,
	Nicky Veitch <nicky.veitch@...cle.com>
Subject: Re: [External] : Re: [bug-report] 5-9% FIO randomwrite ext4 perf
 regression on 6.12.y kernel

On Thu, Nov 21, 2024 at 09:07:32PM +0000, Paul Webb wrote:
> Christoph:
> To check for weird lazy init code using write zeroes
>
> Values in the 5.15 kernel baseline prior to the commit:
> $ cat /sys/block/nvme*n1/queue/write_zeroes_max_bytes
> 0
> 0
> 0
> 0
>
> Values in the 6.11 kernel that contains the commit:
> $ cat /sys/block/nvme*n1/queue/write_zeroes_max_bytes
> 2199023255040
> 2199023255040
> 2199023255040
> 2199023255040

Thanks!  So 6.11 actually enables write zeroes for your controller.

> Another interesting datapoint is that while performing some runs I am 
> seeing the following output on the console in the 6.11/6.12 kernels that 
> contain the commit:
>
> [  473.398188] operation not supported error, dev nvme2n1, sector 13952 op 0x9:(WRITE_ZEROES) flags 0x800 phys_seg 0 prio class 0

.. which it doesn't handle well.

> [  473.534550] nvme0n1: Dataset Management(0x9) @ LBA 14000, 256 blocks, Invalid Command Opcode (sct 0x0 / sc 0x1) DNR

.. and interesting this is for a Deallocate, which should only happen
with the quirk for certain Intel controllers from the very first days of
nvme.

What controller do you have?  Can you post the output of lspci and
"nvme list"?