linux-kernel - Re: [PATCH 0/3] mmc: Improve block layer requeueing behavior

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Message-ID: <c1e1281e-0977-cbf7-041e-db911ee722a7@intel.com>
Date:   Fri, 18 Nov 2022 12:47:29 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Christian Löhle <CLoehle@...erstone.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        Christoph Hellwig <hch@....de>
Cc:     Avri Altman <Avri.Altman@....com>,
        "vincent.whitchurch@...s.com" <vincent.whitchurch@...s.com>
Subject: Re: [PATCH 0/3] mmc: Improve block layer requeueing behavior

On 26/10/22 10:30, Christian Löhle wrote:
> Mmcblk relies on block layer requeueing to fulfill some requests under
> certain conditions. Improve the handling to get nicely ordered requests.
> 
> Using the terms a bit loosely to get a point across:
> Current behavior for 512 blksz and max_blk_count = 1 the scenario would
> be as follows:
> 
> - request for page 0 lba 0 to 7
> - request for page 1 lba 8 to 15
> - request for page 2 lba 16 to 23
> - request for page 3 lba 24 to 31
> 
> mmcblk modifies data->blocks = 1 for each and requeues,
> this leads to:
> 
> Access lba 0
> Access lba 8
> Access lba 16
> Access lba 24
> Access lba 1 (1. Requeue for page 0)
> Access lba 9 (1. Requeue for page 1)
> Access lba 17 (1. Requeue for page 2)
> Access lba 25 (1. Requeue for page 3)
> Access lba 2 (2. Requeue for page 0)
> ...
> 
> Of course we would rather have lbas consecutive.

Does anyone know why the block layer does not support
(max_hw_sectors << 9) < PAGE_SIZE ?