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From: Niklas Schnelle <schnelle@linux.ibm.com>
To: linux-nvme@lists.infradead.org
Cc: Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: [PATCH 0/2] nvme-pic: improve max I/O queue handling
Date: Thu, 12 Nov 2020 09:23:00 +0100	[thread overview]
Message-ID: <20201112082302.82441-1-schnelle@linux.ibm.com> (raw)

Hi,

while searching for a bug around zPCI + NVMe IRQ handling on a distro
kernel, I got confused around handling of the maximum number
of I/O queues in the NVMe driver.
I think I groked it in the end but would like to propose the following
improvements, that said I'm quite new to this code.
I tested both patches on s390x (with a debug config) and x86_64 so
with both data center and consumer NVMes.
For the second patch, since I don't own a device with the quirk, I tried
always returning 1 from nvme_max_io_queues() and confirmed that on my
Evo 970 Pro this resulted in about half the performance in a fio test
but did not otherwise break things. I couldn't find a reason why
allocating only the I/O queues we actually use would be problematic in
the code either but I might have missed something of course.

Best regards,
Niklas Schnelle

Niklas Schnelle (2):
  nvme-pci: drop min() from nr_io_queues assignment
  nvme-pci: don't allocate unused I/O queues

 drivers/nvme/host/pci.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

-- 
2.17.1


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WARNING: multiple messages have this Message-ID (diff)
From: Niklas Schnelle <schnelle@linux.ibm.com>
To: linux-nvme@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, Keith Busch <kbusch@kernel.org>,
	Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>,
	Sagi Grimberg <sagi@grimberg.me>
Subject: [PATCH 0/2] nvme-pic: improve max I/O queue handling
Date: Thu, 12 Nov 2020 09:23:00 +0100	[thread overview]
Message-ID: <20201112082302.82441-1-schnelle@linux.ibm.com> (raw)

Hi,

while searching for a bug around zPCI + NVMe IRQ handling on a distro
kernel, I got confused around handling of the maximum number
of I/O queues in the NVMe driver.
I think I groked it in the end but would like to propose the following
improvements, that said I'm quite new to this code.
I tested both patches on s390x (with a debug config) and x86_64 so
with both data center and consumer NVMes.
For the second patch, since I don't own a device with the quirk, I tried
always returning 1 from nvme_max_io_queues() and confirmed that on my
Evo 970 Pro this resulted in about half the performance in a fio test
but did not otherwise break things. I couldn't find a reason why
allocating only the I/O queues we actually use would be problematic in
the code either but I might have missed something of course.

Best regards,
Niklas Schnelle

Niklas Schnelle (2):
  nvme-pci: drop min() from nr_io_queues assignment
  nvme-pci: don't allocate unused I/O queues

 drivers/nvme/host/pci.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

-- 
2.17.1


             reply	other threads:[~2020-11-12  8:23 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12  8:23 Niklas Schnelle [this message]
2020-11-12  8:23 ` [PATCH 0/2] nvme-pic: improve max I/O queue handling Niklas Schnelle
2020-11-12  8:23 ` [PATCH 1/2] nvme-pci: drop min() from nr_io_queues assignment Niklas Schnelle
2020-11-12  8:23   ` Niklas Schnelle
2020-11-14  9:06   ` Christoph Hellwig
2020-11-14  9:06     ` Christoph Hellwig
2020-11-12  8:23 ` [PATCH 2/2] nvme-pci: don't allocate unused I/O queues Niklas Schnelle
2020-11-12  8:23   ` Niklas Schnelle
2020-11-12 14:53 ` [PATCH 0/2] nvme-pic: improve max I/O queue handling Keith Busch
2020-11-12 14:53   ` Keith Busch
2020-11-12 15:45   ` Niklas Schnelle
2020-11-12 15:45     ` Niklas Schnelle
2020-11-12 17:36     ` Keith Busch
2020-11-12 17:36       ` Keith Busch
2020-11-13 13:15       ` Niklas Schnelle
2020-11-13 13:15         ` Niklas Schnelle
2020-11-13 16:25         ` Christoph Hellwig
2020-11-13 16:25           ` Christoph Hellwig
2020-11-13 16:52           ` Niklas Schnelle
2020-11-13 16:52             ` Niklas Schnelle

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