From: Christoph Hellwig <[email protected]>
To: Kanchan Joshi <[email protected]>
Cc: Christoph Hellwig <[email protected]>,
[email protected], [email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected], [email protected],
[email protected], [email protected], [email protected],
[email protected]
Subject: Re: [PATCH 05/17] nvme: wire-up support for async-passthru on char-device.
Date: Tue, 15 Mar 2022 09:54:10 +0100 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <20220314162356.GA13902@test-zns>
On Mon, Mar 14, 2022 at 09:53:56PM +0530, Kanchan Joshi wrote:
>>> +struct nvme_uring_cmd_pdu {
>>> + u32 meta_len;
>>> + union {
>>> + struct bio *bio;
>>> + struct request *req;
>>> + };
>>> + void *meta; /* kernel-resident buffer */
>>> + void __user *meta_buffer;
>>> +} __packed;
>>
>> Why is this marked __packed?
> Did not like doing it, but had to.
> If not packed, this takes 32 bytes of space. While driver-pdu in struct
> io_uring_cmd can take max 30 bytes. Packing nvme-pdu brought it down to
> 28 bytes, which fits and gives 2 bytes back.
What if you move meta_len to the end? Even if we need the __packed
that will avoid all the unaligned access to pointers, which on some
architectures will crash the kernel.
> And on moving meta elements outside the driver, my worry is that it
> reduces scope of uring-cmd infra and makes it nvme passthru specific.
> At this point uring-cmd is still generic async ioctl/fsctl facility
> which may find other users (than nvme-passthru) down the line. Organization
> of fields within "struct io_uring_cmd" is around the rule
> that a field is kept out (of 28 bytes pdu) only if is accessed by both
> io_uring and driver.
We have plenty of other interfaces of that kind. Sockets are one case
already, and regular read/write with protection information will be
another one. So having some core infrastrucure for "secondary data"
seems very useful.
> I see, so there is room for adding some efficiency.
> Hope it will be ok if I carry this out as a separate effort.
> Since this is about touching blk_mq_complete_request at its heart, and
> improving sync-direct-io, this does not seem best-fit and slow this
> series down.
I really rather to this properly. Especially as the current effort
adds new exported interfaces.
> Deferring by ipi or softirq never occured. Neither for block nor for
> char. Softirq is obvious since I was not running against scsi (or nvme with
> single queue). I could not spot whether this is really a overhead, at
> least for nvme.
This tends to kick in if you have less queues than cpu cores. Quite
command with either a high core cound or a not very high end nvme
controller.
next prev parent reply other threads:[~2022-03-15 8:54 UTC|newest]
Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20220308152651epcas5p1ebd2dc7fa01db43dd587c228a3695696@epcas5p1.samsung.com>
2022-03-08 15:20 ` [PATCH 00/17] io_uring passthru over nvme Kanchan Joshi
[not found] ` <CGME20220308152653epcas5p10c31f58cf6bff125cc0baa176b4d4fac@epcas5p1.samsung.com>
2022-03-08 15:20 ` [PATCH 01/17] io_uring: add support for 128-byte SQEs Kanchan Joshi
[not found] ` <CGME20220308152655epcas5p4ae47d715e1c15069e97152dcd283fd40@epcas5p4.samsung.com>
2022-03-08 15:20 ` [PATCH 02/17] fs: add file_operations->async_cmd() Kanchan Joshi
[not found] ` <CGME20220308152658epcas5p3929bd1fcf75edc505fec71901158d1b5@epcas5p3.samsung.com>
2022-03-08 15:20 ` [PATCH 03/17] io_uring: add infra and support for IORING_OP_URING_CMD Kanchan Joshi
2022-03-11 1:51 ` Luis Chamberlain
2022-03-11 2:43 ` Jens Axboe
2022-03-11 17:11 ` Luis Chamberlain
2022-03-11 18:47 ` Paul Moore
2022-03-11 20:57 ` Luis Chamberlain
2022-03-11 21:03 ` Paul Moore
2022-03-14 16:25 ` Casey Schaufler
2022-03-14 16:32 ` Luis Chamberlain
2022-03-14 18:05 ` Casey Schaufler
2022-03-14 19:40 ` Luis Chamberlain
[not found] ` <CGME20220308152700epcas5p4130d20119a3a250a2515217d6552f668@epcas5p4.samsung.com>
2022-03-08 15:20 ` [PATCH 04/17] nvme: modify nvme_alloc_request to take an additional parameter Kanchan Joshi
2022-03-11 6:38 ` Christoph Hellwig
[not found] ` <CGME20220308152702epcas5p1eb1880e024ac8b9531c85a82f31a4e78@epcas5p1.samsung.com>
2022-03-08 15:20 ` [PATCH 05/17] nvme: wire-up support for async-passthru on char-device Kanchan Joshi
2022-03-10 0:02 ` Clay Mayers
2022-03-10 8:32 ` Kanchan Joshi
2022-03-11 7:01 ` Christoph Hellwig
2022-03-14 16:23 ` Kanchan Joshi
2022-03-15 8:54 ` Christoph Hellwig [this message]
2022-03-16 7:27 ` Kanchan Joshi
2022-03-24 6:22 ` Christoph Hellwig
2022-03-24 17:45 ` Kanchan Joshi
2022-03-11 17:56 ` Luis Chamberlain
2022-03-11 18:53 ` Paul Moore
2022-03-11 21:02 ` Luis Chamberlain
2022-03-13 21:53 ` Sagi Grimberg
2022-03-14 17:54 ` Kanchan Joshi
2022-03-15 9:02 ` Sagi Grimberg
2022-03-16 9:21 ` Kanchan Joshi
2022-03-16 10:56 ` Sagi Grimberg
2022-03-16 11:51 ` Kanchan Joshi
2022-03-16 13:52 ` Sagi Grimberg
2022-03-16 14:35 ` Jens Axboe
2022-03-16 14:50 ` Sagi Grimberg
2022-03-24 6:20 ` Christoph Hellwig
2022-03-24 10:42 ` Sagi Grimberg
2022-03-22 15:18 ` Clay Mayers
2022-03-22 16:57 ` Kanchan Joshi
[not found] ` <CGME20220308152704epcas5p16610e1f50672b25fa1df5f7c5c261bb5@epcas5p1.samsung.com>
2022-03-08 15:20 ` [PATCH 06/17] io_uring: prep for fixed-buffer enabled uring-cmd Kanchan Joshi
[not found] ` <CGME20220308152707epcas5p430127761a7fd4bf90c2501eabe9ee96e@epcas5p4.samsung.com>
2022-03-08 15:20 ` [PATCH 07/17] io_uring: add support for uring_cmd with fixed-buffer Kanchan Joshi
[not found] ` <CGME20220308152709epcas5p1f9d274a0214dc462c22c278a72d8697c@epcas5p1.samsung.com>
2022-03-08 15:20 ` [PATCH 08/17] nvme: enable passthrough " Kanchan Joshi
2022-03-10 8:32 ` Christoph Hellwig
2022-03-11 6:43 ` Christoph Hellwig
2022-03-14 13:06 ` Kanchan Joshi
2022-03-15 8:55 ` Christoph Hellwig
2022-03-14 12:18 ` Ming Lei
2022-03-14 13:09 ` Kanchan Joshi
[not found] ` <CGME20220308152711epcas5p31de5d63f5de91fae94e61e5c857c0f13@epcas5p3.samsung.com>
2022-03-08 15:20 ` [PATCH 09/17] io_uring: plug for async bypass Kanchan Joshi
2022-03-10 8:33 ` Christoph Hellwig
2022-03-14 14:33 ` Ming Lei
2022-03-15 8:56 ` Christoph Hellwig
2022-03-11 17:15 ` Luis Chamberlain
[not found] ` <CGME20220308152714epcas5p4c5a0d16512fd7054c9a713ee28ede492@epcas5p4.samsung.com>
2022-03-08 15:20 ` [PATCH 10/17] block: wire-up support for plugging Kanchan Joshi
2022-03-10 8:34 ` Christoph Hellwig
2022-03-10 12:40 ` Kanchan Joshi
2022-03-14 14:40 ` Ming Lei
2022-03-21 7:02 ` Kanchan Joshi
2022-03-23 1:27 ` Ming Lei
2022-03-23 1:41 ` Jens Axboe
2022-03-23 1:58 ` Jens Axboe
2022-03-23 2:10 ` Ming Lei
2022-03-23 2:17 ` Jens Axboe
[not found] ` <CGME20220308152716epcas5p3d38d2372c184259f1a10c969f7e4396f@epcas5p3.samsung.com>
2022-03-08 15:20 ` [PATCH 11/17] block: factor out helper for bio allocation from cache Kanchan Joshi
2022-03-10 8:35 ` Christoph Hellwig
2022-03-10 12:25 ` Kanchan Joshi
2022-03-24 6:30 ` Christoph Hellwig
2022-03-24 17:45 ` Kanchan Joshi
2022-03-25 5:38 ` Christoph Hellwig
[not found] ` <CGME20220308152718epcas5p3afd2c8a628f4e9733572cbb39270989d@epcas5p3.samsung.com>
2022-03-08 15:21 ` [PATCH 12/17] nvme: enable bio-cache for fixed-buffer passthru Kanchan Joshi
2022-03-11 6:48 ` Christoph Hellwig
2022-03-14 18:18 ` Kanchan Joshi
2022-03-15 8:57 ` Christoph Hellwig
[not found] ` <CGME20220308152720epcas5p19653942458e160714444942ddb8b8579@epcas5p1.samsung.com>
2022-03-08 15:21 ` [PATCH 13/17] nvme: allow user passthrough commands to poll Kanchan Joshi
2022-03-08 17:08 ` Keith Busch
2022-03-09 7:03 ` Kanchan Joshi
2022-03-11 6:49 ` Christoph Hellwig
[not found] ` <CGME20220308152723epcas5p34460b4af720e515317f88dbb78295f06@epcas5p3.samsung.com>
2022-03-08 15:21 ` [PATCH 14/17] io_uring: add polling support for uring-cmd Kanchan Joshi
2022-03-11 6:50 ` Christoph Hellwig
2022-03-14 10:16 ` Kanchan Joshi
2022-03-15 8:57 ` Christoph Hellwig
2022-03-16 5:09 ` Kanchan Joshi
2022-03-24 6:30 ` Christoph Hellwig
[not found] ` <CGME20220308152725epcas5p36d1ce3269a47c1c22cc0d66bdc2b9eb3@epcas5p3.samsung.com>
2022-03-08 15:21 ` [PATCH 15/17] nvme: wire-up polling for uring-passthru Kanchan Joshi
[not found] ` <CGME20220308152727epcas5p20e605718dd99e97c94f9232d40d04d95@epcas5p2.samsung.com>
2022-03-08 15:21 ` [PATCH 16/17] io_uring: add support for non-inline uring-cmd Kanchan Joshi
[not found] ` <CGME20220308152729epcas5p17e82d59c68076eb46b5ef658619d65e3@epcas5p1.samsung.com>
2022-03-08 15:21 ` [PATCH 17/17] nvme: enable non-inline passthru commands Kanchan Joshi
2022-03-10 8:36 ` Christoph Hellwig
2022-03-10 11:50 ` Kanchan Joshi
2022-03-10 14:19 ` Christoph Hellwig
2022-03-10 18:43 ` Kanchan Joshi
2022-03-11 6:27 ` Christoph Hellwig
2022-03-22 17:10 ` Kanchan Joshi
2022-03-24 6:32 ` Christoph Hellwig
2022-03-25 13:39 ` Kanchan Joshi
2022-03-28 4:44 ` Kanchan Joshi
2022-03-30 12:59 ` Christoph Hellwig
2022-03-30 13:02 ` Christoph Hellwig
2022-03-30 13:14 ` Kanchan Joshi
2022-04-01 1:25 ` Jens Axboe
2022-04-01 2:33 ` Kanchan Joshi
2022-04-01 2:44 ` Jens Axboe
2022-04-01 3:05 ` Jens Axboe
2022-04-01 6:32 ` Kanchan Joshi
2022-04-19 17:31 ` Kanchan Joshi
2022-04-19 18:19 ` Jens Axboe
[not found] ` <CGME20220420152003epcas5p3991e6941773690bcb425fd9d817105c3@epcas5p3.samsung.com>
2022-04-20 15:14 ` Kanchan Joshi
2022-04-20 15:28 ` Kanchan Joshi
2022-04-01 1:23 ` Jens Axboe
2022-04-01 1:22 ` Jens Axboe
2022-04-01 6:29 ` Kanchan Joshi
2022-03-24 21:09 ` Clay Mayers
2022-03-24 23:36 ` Jens Axboe
2022-03-10 8:29 ` [PATCH 00/17] io_uring passthru over nvme Christoph Hellwig
2022-03-10 10:05 ` Kanchan Joshi
2022-03-11 16:43 ` Luis Chamberlain
2022-03-11 23:35 ` Adam Manzanares
2022-03-12 2:27 ` Adam Manzanares
2022-03-13 5:07 ` Kanchan Joshi
2022-03-14 20:30 ` Adam Manzanares
2022-03-13 5:10 ` Kanchan Joshi
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