linux-kernel - Re: [PATCH] scsi: ibmvscsi_tgt: Use dma_alloc_coherent() instead of get_zeroed_page/dma_map

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Message-ID: <YWPc1GxFiOloHveI@infradead.org>
Date:   Mon, 11 Oct 2021 07:42:28 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Cai Huoqing <caihuoqing@...du.com>
Cc:     Michael Cyr <mikecyr@...ux.ibm.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: ibmvscsi_tgt: Use dma_alloc_coherent() instead of
 get_zeroed_page/dma_map_single()

On Mon, Oct 11, 2021 at 12:00:53AM +0800, Cai Huoqing wrote:
> Replacing get_zeroed_page/free_page/dma_map_single/dma_unmap_single()
> with dma_alloc_coherent/dma_free_coherent() helps to reduce
> code size, and simplify the code, and coherent DMA will not
> clear the cache every time.

This explanation does not make any sense whatsoever.  Please explain
why it would an show numbers.