Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <338207c2-e3cd-abc1-6b8c-f08645ef144a@kernel.dk>
Date:   Tue, 29 Mar 2022 08:41:57 -0600
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101
 Thunderbird/91.7.0
Subject: Re: [PATCH -next RFC 2/6] block: refactor to split bio thoroughly
Content-Language: en-US
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Yu Kuai <yukuai3@huawei.com>, andriy.shevchenko@linux.intel.com,
        john.garry@huawei.com, ming.lei@redhat.com,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com
References: <20220329094048.2107094-1-yukuai3@huawei.com>
 <20220329094048.2107094-3-yukuai3@huawei.com>
 <YkMKgwsZ3K8dRVbX@infradead.org>
 <e46db33f-84a6-6d23-9be2-7429fec71046@kernel.dk>
 <YkMabVKr+7Mg53E1@infradead.org>
From:   Jens Axboe <axboe@kernel.dk>
In-Reply-To: <YkMabVKr+7Mg53E1@infradead.org>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 3/29/22 8:40 AM, Christoph Hellwig wrote:
> On Tue, Mar 29, 2022 at 08:35:29AM -0600, Jens Axboe wrote:
>>> But more importantly why does your use case even have splits that get
>>> submitted together?  Is this a case of Linus' stupidly low default
>>> max_sectors when the hardware supports more, or is the hardware limited
>>> to a low number of sectors per request?  Or do we hit another reason
>>> for the split?
>>
>> See the posted use case, it's running 512kb ios on a 128kb device.
> 
> That is an awfully low limit these days.  I'm really not sure we should
> optimize the block layer for that.

That's exactly what my replies have been saying. I don't think this is
a relevant thing to optimize for.

Fixing fairness for wakeups seems useful, however.

-- 
Jens Axboe