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

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Message-ID: <3decbaf1-250b-9b73-70fd-4cb9a204c452@kernel.dk>
Date:   Thu, 27 Apr 2023 17:01:04 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Chaitanya Kulkarni <chaitanyak@...dia.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sagi Grimberg <sagi@...mberg.me>,
        Christoph Hellwig <hch@....de>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH] nvmet: Reorder fields in 'struct nvmet_ns'

On 4/27/23 4:59?PM, Chaitanya Kulkarni wrote:
> On 4/27/23 12:47, Christophe JAILLET wrote:
>> Group some variables based on their sizes to reduce holes.
>> On x86_64, this shrinks the size of 'struct nvmet_ns' from 520 to 512
>> bytes.
>>
> 
> Although this looks good, we at least need to document what
> happens on other arch(s) which are not mentioned in the
> commit log ? is there a possibility that someone might come
> up with the contradictory data in future for the arch(s) which
> arch that are not mentioned here ?

The change is certainly not going to make things _worse_ for any arch,
so I think that's somewhat of a pointless exercise and an unreasonable
ask for something that makes sense on 64-bit arm/x86 and saves half the
space.

-- 
Jens Axboe