linux-kernel - Re: [PATCH] nvmet: Reorder fields in 'struct nvmet

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Message-ID: <f1aea5d9-ca7b-ecf4-b162-cf760eafbe6c@nvidia.com>
Date:   Fri, 28 Apr 2023 08:11:28 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sagi Grimberg <sagi@...mberg.me>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "kbusch@...nel.org" <kbusch@...nel.org>
Subject: Re: [PATCH] nvmet: Reorder fields in 'struct nvmet_ns'

On 4/28/23 00:33, Christophe JAILLET wrote:
> Le 28/04/2023 à 01:12, Chaitanya Kulkarni a écrit :
>> (+Keith, for host side)
>>> ---
>>> More aggressive grouping could be done to be more future proof, but the
>>> way the struct nvmet_ns is written suggest that some fields should be
>>> kept together. So keep grouping as-is.
>>>
>>>
>>
>> you can send RFC and I'll be happy to take a look if it's going
>> have any benefit, it will take some time though..
>>
>> for host side :-
>>
>> while you are at it, it might be useful to take a look at the structures
>> that are accessed in the fast path on the host side ?
>
> Ok, why not, but can you help identifying these structures or places 
> considered as fast path?
>
> CJ

you can start with nvme_ns/nvme_ctrl as I remember nvme_ns is used
in nvme_setup_rw_cmd() on host and nvme_ctrl is used in
nvmet_passthru_execute_cmd().

In general nvme_queue_rq()/nvme_rdma_queue_rq()/
nvmet_bdev_execute_rw()/nvmet_file_execute_rw()/
nvmet_passthru_execute_cmd() are functions to start with, then you can
see structs starting with nvme_ prefix (mainly related to ns and ctrl)
which are worth taking a look and their benefits, but be careful what
you are moving ...

Ohh and nvmet_req that is also ...

-ck