linux-kernel - Re: [PATCH v2 3/3] scsi/ncr5380: Improve interrupt latency during PIO tranfers

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Message-ID: <yq1twdil59u.fsf@sermon.lab.mkp.net>
Date:   Wed, 14 Sep 2016 14:12:29 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Finn Thain <fthain@...egraphics.com.au>
Cc:     "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        <linux-scsi@...r.kernel.org>, <linux-m68k@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Michael Schmitz <schmitzmic@...il.com>
Subject: Re: [PATCH v2 3/3] scsi/ncr5380: Improve interrupt latency during PIO tranfers

>>>>> "Finn" == Finn Thain <fthain@...egraphics.com.au> writes:

Finn> Large PIO transfers are broken up into chunks to try to avoid
Finn> disabling local IRQs for long periods. But IRQs are still disabled
Finn> for too long and this causes SCC FIFO overruns during serial port
Finn> transfers.

Finn> This patch reduces the PIO chunk size to reduce interrupt latency
Finn> to something on the order of milliseconds, at the expense of
Finn> additional CPU overhead from extra iterations of the
Finn> NCR5380_main() loop.

Applied to 4.9/scsi-queue.

-- 
Martin K. Petersen	Oracle Linux Engineering