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

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Date:	Fri, 26 Nov 2010 15:00:49 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Mark Lord <kernel@...savvy.com>
cc:	Greg Freemyer <greg.freemyer@...il.com>,
	"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 Fri, 26 Nov 2010, Mark Lord wrote:

> On 10-11-25 11:24 AM, Greg Freemyer wrote:
> > 
> > I'm away from my systems today, but is there an easy way to tweak
> > wiper.sh or hdparm to cause only a single range per trim command.
> > 
> > I'm curious if for the Sandforce that would still be in the 90 second
> > range, or closer to 64x that.
> 
> Good question.  The Indilinx based drives would be in the 64x range,
> no doubt there.  But I don't know about the Sandforce.
> 
> And I don't think I'm willing to inflict so many life-shortening erase
> cycles onto it just to find out.
> 
> One thing to note:  the execution time for TRIM does vary depending upon
> whether the (logical) LBAs are already mostly in a "trimmed" state or not.
> 
> So anyone aspiring to benchmark this stuff will need to keep that in mind.
> My timings above were for "already trimmed" cases.  I would expect them
> to be much slower (2x - 3x) if the sectors all held data prior to trim.
> 
> Cheers
> 

I have already did some TRIM benchmarking, but especially regarding trim
extent size. Also there is a tool test-discard for that purpose, so it
may be handy for anyone trying to do something similar.

http://people.redhat.com/lczerner/discard/

Thanks!

-Lukas
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