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To:     Long Li <longli@linuxonhyperv.com>
Cc:     "K . Y . Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "James E . J . Bottomley" <JBottomley@odin.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        devel@linuxdriverproject.org, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, longli@microsoft.com
Subject: Re: [Patch v2] Storvsc: Select channel based on available percentage of ring buffer to write
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
References: <20180419215424.3557-1-longli@linuxonhyperv.com>
Date:   Fri, 20 Apr 2018 15:40:11 -0400
In-Reply-To: <20180419215424.3557-1-longli@linuxonhyperv.com> (Long Li's
        message of "Thu, 19 Apr 2018 14:54:24 -0700")
Message-ID: <yq1bmedis4k.fsf@oracle.com>
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Long,

> This is a best effort for estimating on how busy the ring buffer is
> for that channel, based on available buffer to write in percentage. It
> is still possible that at the time of actual ring buffer write, the
> space may not be available due to other processes may be writing at
> the time.
>
> Selecting a channel based on how full it is can reduce the possibility
> that a ring buffer write will fail, and avoid the situation a channel
> is over busy.
>
> Now it's possible that storvsc can use a smaller ring buffer size
> (e.g. 40k bytes) to take advantage of cache locality.

Applied to 4.18/scsi-queue. Thank you!

-- 
Martin K. Petersen	Oracle Linux Engineering