linux-kernel - Re: [PATCH v2] scsi: hisi_sas: optimise DMA slot memory

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Message-ID: <yq137afx3w5.fsf@oracle.com>
Date:   Sat, 01 Jul 2017 17:07:22 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     John Garry <john.garry@...wei.com>
Cc:     <jejb@...ux.vnet.ibm.com>, <martin.petersen@...cle.com>,
        <linuxarm@...wei.com>, <linux-scsi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Xiaofei Tan <tanxiaofei@...wei.com>
Subject: Re: [PATCH v2] scsi: hisi_sas: optimise DMA slot memory


John,

> Currently we allocate 3 sets of DMA memories from separate
> pools for each slot. This is inefficient in terms of memory usage
> (buffers are less than 1 page in size, so we lose due to alignment),
> and also time spent in doing 3 allocations + de-allocations per slot,
> instead of 1.
>
> To optimise, combine the 3 DMA buffers into a single buffer from a
> single pool.

Applied to 4.13/scsi-queue. Thank you!

-- 
Martin K. Petersen	Oracle Linux Engineering