linux-kernel - Re: Discard support (was Re: [PATCH] swap: send callback when swap slot is freed)

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Message-ID: <4A89BB5B.5060403@rtr.ca>
Date:	Mon, 17 Aug 2009 16:19:39 -0400
From:	Mark Lord <liml@....ca>
To:	James Bottomley <James.Bottomley@...e.de>
Cc:	Greg Freemyer <greg.freemyer@...il.com>,
	Bill Davidsen <davidsen@....com>,
	Arjan van de Ven <arjan@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Chris Worley <worleys@...il.com>,
	Matthew Wilcox <matthew@....cx>,
	Bryan Donlan <bdonlan@...il.com>, david@...g.hm,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Nitin Gupta <ngupta@...are.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-scsi@...r.kernel.org, linux-ide@...r.kernel.org,
	Linux RAID <linux-raid@...r.kernel.org>
Subject: Re: Discard support (was Re: [PATCH] swap: send callback when swap
  slot is freed)

James Bottomley wrote:
> On Mon, 2009-08-17 at 14:21 -0400, Greg Freemyer wrote:
>> On Mon, Aug 17, 2009 at 1:19 PM, James Bottomley<James.Bottomley@...e.de> wrote:
>>> On Mon, 2009-08-17 at 13:08 -0400, Greg Freemyer wrote:
..
>>>> Non-coalescing is believed detrimental,
>>> It is?  Why?
>> For the only compliant SSD in the wild, Mark has shown it to be true
>> via testing.
> 
> He only said larger trims take longer.  As I said previously, if it's a
> X+nY relationship, then we still benefit from accumulation up to some
> value of n.
..

Err, what I said was, "rm -rf /usr/src/linux" takes over half an hour
with uncoalesced TRIM, and only a scant few seconds in total *with*
coalesced TRIM.


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