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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-nvme@lists.infradead.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	Wen Xiong <wenxiong@linux.ibm.com>,
	Keith Busch <kbusch@kernel.org>,
	linuxppc-dev@lists.ozlabs.org, Dave Young <dyoung@redhat.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	Baoquan He <bhe@redhat.com>, Pingfan Liu <piliu@redhat.com>
Subject: Re: [PATCH V3 01/14] blk-mq: add blk_mq_max_nr_hw_queues()
Date: Thu, 10 Aug 2023 08:09:27 +0800	[thread overview]
Message-ID: <ZNQqt1C0pXspGl3d@fedora> (raw)
In-Reply-To: <20230809134401.GA31852@lst.de>

On Wed, Aug 09, 2023 at 03:44:01PM +0200, Christoph Hellwig wrote:
> I'm starting to sound like a broken record, but we can't just do random
> is_kdump checks, and it's not going to get better by resending it again and
> again.  If kdump kernels limit the number of possible CPUs, it needs to
> reflected in cpu_possible_map and we need to use that information.
> 

Can you look at previous kdump/arch guys' comment about kdump usage &
num_possible_cpus?

    https://lore.kernel.org/linux-block/CAF+s44RuqswbosY9kMDx35crviQnxOeuvgNsuE75Bb0Y2Jg2uw@mail.gmail.com/
    https://lore.kernel.org/linux-block/ZKz912KyFQ7q9qwL@MiWiFi-R3L-srv/

The point is that kdump kernels does not limit the number of possible CPUs.

1) some archs support 'nr_cpus=1' for kdump kernel, which is fine, since
num_possible_cpus becomes 1.

2) some archs do not support 'nr_cpus=1', and have to rely on
'max_cpus=1', so num_possible_cpus isn't changed, and kernel just boots
with single online cpu. That causes trouble because blk-mq limits single
queue.

Documentation/admin-guide/kdump/kdump.rst

Thanks, 
Ming


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kexec@lists.infradead.org
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WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-nvme@lists.infradead.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	Wen Xiong <wenxiong@linux.ibm.com>,
	Keith Busch <kbusch@kernel.org>,
	linuxppc-dev@lists.ozlabs.org, Dave Young <dyoung@redhat.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	Baoquan He <bhe@redhat.com>, Pingfan Liu <piliu@redhat.com>
Subject: Re: [PATCH V3 01/14] blk-mq: add blk_mq_max_nr_hw_queues()
Date: Thu, 10 Aug 2023 08:09:27 +0800	[thread overview]
Message-ID: <ZNQqt1C0pXspGl3d@fedora> (raw)
In-Reply-To: <20230809134401.GA31852@lst.de>

On Wed, Aug 09, 2023 at 03:44:01PM +0200, Christoph Hellwig wrote:
> I'm starting to sound like a broken record, but we can't just do random
> is_kdump checks, and it's not going to get better by resending it again and
> again.  If kdump kernels limit the number of possible CPUs, it needs to
> reflected in cpu_possible_map and we need to use that information.
> 

Can you look at previous kdump/arch guys' comment about kdump usage &
num_possible_cpus?

    https://lore.kernel.org/linux-block/CAF+s44RuqswbosY9kMDx35crviQnxOeuvgNsuE75Bb0Y2Jg2uw@mail.gmail.com/
    https://lore.kernel.org/linux-block/ZKz912KyFQ7q9qwL@MiWiFi-R3L-srv/

The point is that kdump kernels does not limit the number of possible CPUs.

1) some archs support 'nr_cpus=1' for kdump kernel, which is fine, since
num_possible_cpus becomes 1.

2) some archs do not support 'nr_cpus=1', and have to rely on
'max_cpus=1', so num_possible_cpus isn't changed, and kernel just boots
with single online cpu. That causes trouble because blk-mq limits single
queue.

Documentation/admin-guide/kdump/kdump.rst

Thanks, 
Ming


WARNING: multiple messages have this Message-ID (diff)
From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Pingfan Liu <piliu@redhat.com>, Dave Young <dyoung@redhat.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	Wen Xiong <wenxiong@linux.ibm.com>, Baoquan He <bhe@redhat.com>,
	Keith Busch <kbusch@kernel.org>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH V3 01/14] blk-mq: add blk_mq_max_nr_hw_queues()
Date: Thu, 10 Aug 2023 08:09:27 +0800	[thread overview]
Message-ID: <ZNQqt1C0pXspGl3d@fedora> (raw)
In-Reply-To: <20230809134401.GA31852@lst.de>

On Wed, Aug 09, 2023 at 03:44:01PM +0200, Christoph Hellwig wrote:
> I'm starting to sound like a broken record, but we can't just do random
> is_kdump checks, and it's not going to get better by resending it again and
> again.  If kdump kernels limit the number of possible CPUs, it needs to
> reflected in cpu_possible_map and we need to use that information.
> 

Can you look at previous kdump/arch guys' comment about kdump usage &
num_possible_cpus?

    https://lore.kernel.org/linux-block/CAF+s44RuqswbosY9kMDx35crviQnxOeuvgNsuE75Bb0Y2Jg2uw@mail.gmail.com/
    https://lore.kernel.org/linux-block/ZKz912KyFQ7q9qwL@MiWiFi-R3L-srv/

The point is that kdump kernels does not limit the number of possible CPUs.

1) some archs support 'nr_cpus=1' for kdump kernel, which is fine, since
num_possible_cpus becomes 1.

2) some archs do not support 'nr_cpus=1', and have to rely on
'max_cpus=1', so num_possible_cpus isn't changed, and kernel just boots
with single online cpu. That causes trouble because blk-mq limits single
queue.

Documentation/admin-guide/kdump/kdump.rst

Thanks, 
Ming


  reply	other threads:[~2023-08-10  0:09 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-08 10:42 [PATCH V3 0/14] blk-mq: fix wrong queue mapping for kdump kernel Ming Lei
2023-08-08 10:42 ` [PATCH V3 01/14] blk-mq: add blk_mq_max_nr_hw_queues() Ming Lei
2023-08-09 13:44   ` Christoph Hellwig
2023-08-10  0:09     ` Ming Lei [this message]
2023-08-10  0:09       ` Ming Lei
2023-08-10  0:09       ` Ming Lei
2023-08-10  1:18       ` Baoquan He
2023-08-10  1:18         ` Baoquan He
2023-08-10  1:18         ` Baoquan He
2023-08-10  2:06         ` Ming Lei
2023-08-10  2:06           ` Ming Lei
2023-08-10  2:06           ` Ming Lei
2023-08-10  3:01           ` Baoquan He
2023-08-10  3:01             ` Baoquan He
2023-08-10  3:01             ` Baoquan He
2023-08-11  7:53             ` Hari Bathini
2023-08-11  7:53               ` Hari Bathini
2023-08-11  7:53               ` Hari Bathini
2023-09-05  5:03               ` Baoquan He
2023-09-05  5:03                 ` Baoquan He
2023-09-05  5:03                 ` Baoquan He
2023-08-11 13:10       ` Christoph Hellwig
2023-08-11 13:10         ` Christoph Hellwig
2023-08-11 13:10         ` Christoph Hellwig
2023-08-08 10:42 ` [PATCH V3 02/14] nvme-pci: use blk_mq_max_nr_hw_queues() to calculate io queues Ming Lei
2023-08-08 10:42 ` [PATCH V3 03/14] ublk: limit max allowed nr_hw_queues Ming Lei
2023-08-08 10:42 ` [PATCH V3 04/14] virtio-blk: limit max allowed submit queues Ming Lei
2023-08-08 10:42   ` Ming Lei
2023-08-10 19:23   ` Michael S. Tsirkin
2023-08-10 19:23     ` Michael S. Tsirkin
2023-08-08 10:42 ` [PATCH V3 05/14] scsi: core: add helper of scsi_max_nr_hw_queues() Ming Lei
2023-08-08 10:42 ` [PATCH V3 06/14] scsi: lpfc: use blk_mq_max_nr_hw_queues() to calculate io vectors Ming Lei
2023-08-08 10:42 ` [PATCH V3 07/14] scsi: mpi3mr: take blk_mq_max_nr_hw_queues() into account for calculating " Ming Lei
2023-08-08 10:42 ` [PATCH V3 08/14] scsi: megaraid: " Ming Lei
2023-08-08 10:42 ` [PATCH V3 09/14] scsi: mpt3sas: " Ming Lei
2023-08-08 10:42 ` [PATCH V3 10/14] scsi: pm8001: " Ming Lei
2023-08-08 10:42 ` [PATCH V3 11/14] scsi: hisi: " Ming Lei
2023-08-08 10:42 ` [PATCH V3 12/14] scsi: ufs: limit max allowed nr_hw_queues Ming Lei
2023-08-08 10:42 ` [PATCH V3 13/14] scsi: storvsc: " Ming Lei
2023-08-08 10:42 ` [PATCH V3 14/14] blk-mq: add helpers for treating kdump kernel Ming Lei
2023-08-10  8:00   ` kernel test robot

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