From: Jeff Garzik <jeff@garzik.org>
To: Mark Lord <liml@rtr.ca>
Cc: "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
Tejun Heo <htejun@gmail.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
Jens Axboe <axboe@suse.de>, Hannes Reinecke <hare@suse.de>
Subject: Re: jgarzik and max-sectors: out of memory
Date: Sat, 27 May 2006 16:02:06 -0400 [thread overview]
Message-ID: <4478B03E.9060202@garzik.org> (raw)
In-Reply-To: <4478AD4B.5090404@rtr.ca>
Mark Lord wrote:
> Jeff Garzik wrote:
> ..
>> Further -- someone with a long ATA memory correct me -- I think that
>> we can increase ATA_MAX_PRD beyond 256. Most DMA engines should just
>> keep chugging along, provided that we continue to respect the 64k IDE
>> DMA boundaries.
>
> MAX_PRD used to be equal to MAX_SECTORS, as that's the worst case scenario.
Not for lba48, which has a larger max-sectors but is still clamped to
the same 256 PRD entries...
> The only real gotcha I remember from the original IDE driver,
> was that some (very few) controllers were buggy with handing
> of a sector_count of zero (256), so setting the limit to a slightly
> lower value prevented that from ever being a problem.
Yeah, a couple of Alan's PATA drivers are fixed at 255.
> That was in the days before the block layer could limit the segment count.
Ahhhhh, useful to know.
Jeff
next prev parent reply other threads:[~2006-05-27 20:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-27 19:37 jgarzik and max-sectors: out of memory Jeff Garzik
2006-05-27 19:49 ` Mark Lord
2006-05-27 20:02 ` Jeff Garzik [this message]
2006-05-27 20:43 ` Jens Axboe
2006-05-30 4:58 ` Jeff Garzik
2006-05-30 8:36 ` Jens Axboe
2006-05-30 9:02 ` Jeff Garzik
2006-05-30 9:10 ` Jens Axboe
2006-05-30 9:15 ` Jeff Garzik
2006-05-30 9:25 ` Jens Axboe
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