linux-ext4 - Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super

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Date:	Thu, 25 Nov 2010 09:44:15 -0500
From:	Mark Lord <kernel@...savvy.com>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
CC:	Ted Ts'o <tytso@....edu>, Lukas Czerner <lczerner@...hat.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	James Bottomley <James.Bottomley@...e.de>,
	Christoph Hellwig <hch@...radead.org>,
	Matthew Wilcox <matthew@....cx>,
	Josef Bacik <josef@...hat.com>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	sandeen@...hat.com
Subject: Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation

On 10-11-24 11:23 PM, Martin K. Petersen wrote:
>>>>>> "Mark" == Mark Lord<kernel@...savvy.com>  writes:
>
> Mark>  But mke2fs probably is NOT doing a "single big discard", because
> Mark>  for SATA the TRIM command is limited to 64K sectors per
> Mark>  range.. and the in-kernel TRIM code only ever does single ranges..
>
> How many times must I reiterate that this is not true?

> Due to various limitations in the way the block layer works we can not
> clear LBA 10 to 20 and LBA 40 to 50 in one command. We don't have an
> infrastructure in place that allows us to operate on several discrete
> areas in one request.
>
> But for contiguous areas we will cram as many ranges entries in as we
> can fit in the TRIM payload. This means we'll issue one TRIM command for
> every 2 GiB minus change (65535*64*512 / 1048576 = 2047 MiB).

Once, will do, thanks.
That's the first time I've read it here with sufficient explanation.
You have my apologies if you've attempted it earlier.

Thanks!
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