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Re: [dm-devel] [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush
- From: Hannes Reinecke <hare suse de>
- To: Christoph Hellwig <hch lst de>
- Cc: "tytso mit edu" <tytso mit edu>, "linux-scsi vger kernel org" <linux-scsi vger kernel org>, "linux-ide vger kernel org" <linux-ide vger kernel org>, Jens Axboe <jaxboe fusionio com>, "jack suse cz" <jack suse cz>, "linux-kernel vger kernel org" <linux-kernel vger kernel org>, "linux-raid vger kernel org" <linux-raid vger kernel org>, "linux-fsdevel vger kernel org" <linux-fsdevel vger kernel org>, "dm-devel redhat com" <dm-devel redhat com>, "James Bottomley suse de" <James Bottomley suse de>, "konishi ryusuke lab ntt co jp" <konishi ryusuke lab ntt co jp>, Tejun Heo <tj kernel org>, "vst vlnb net" <vst vlnb net>, Ric Wheeler <rwheeler redhat com>, "swhiteho redhat com" <swhiteho redhat com>, "chris mason oracle com" <chris mason oracle com>
- Subject: Re: [dm-devel] [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush
- Date: Mon, 30 Aug 2010 12:04:56 +0200
Christoph Hellwig wrote:
> On Mon, Aug 23, 2010 at 04:01:15PM +0200, Jens Axboe wrote:
>> The problem purely exists on arrays that report write back cache enabled
>> AND don't implement SYNC_CACHE as a noop. Do any of them exist, or are
>> they purely urban legend?
>
> I haven't seen it. I don't care particularly about this case, but once
> it a while people want to disable flushing for testing or because they
> really don't care.
>
aacraid for one falls into this category.
SYNC_CACHE is no-oped in the driver. Otherwise you get a _HUGE_
performance loss.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare suse de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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