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From: Hannes Reinecke <>
To: Matthew Wilcox <>,
	Naohiro Aota <>
	Andrew Morton <>
Subject: Re: Project idea: Swap to zoned block devices
Date: Tue, 15 Oct 2019 15:48:47 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 10/15/19 1:35 PM, Matthew Wilcox wrote:
> On Tue, Oct 15, 2019 at 01:38:27PM +0900, Naohiro Aota wrote:
>> A zoned block device consists of a number of zones. Zones are
>> either conventional and accepting random writes or sequential and
>> requiring that writes be issued in LBA order from each zone write
>> pointer position. For the write restriction, zoned block devices are
>> not suitable for a swap device. Disallow swapon on them.
> That's unfortunate.  I wonder what it would take to make the swap code be
> suitable for zoned devices.  It might even perform better on conventional
> drives since swapout would be a large linear write.  Swapin would be a
> fragmented, seeky set of reads, but this would seem like an excellent
> university project.
The main problem I'm seeing is the eviction of pages from swap.
While swapin is easy (as you can do random access on reads), evict pages
from cache becomes extremely tricky as you can only delete entire zones.
So how to we mark pages within zones as being stale?
Or can we modify the swapin code to always swap in an entire zone and
discard it immediately?


Dr. Hannes Reinecke		      Teamlead Storage & Networking			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 247165 (AG München), GF: Felix Imendörffer

  parent reply	other threads:[~2019-10-15 13:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-15  4:38 [PATCH] mm, swap: disallow swapon() on zoned block devices Naohiro Aota
2019-10-15  7:57 ` Christoph Hellwig
2019-10-15  8:58 ` [PATCH v2] " Naohiro Aota
2019-10-15  9:06   ` Christoph Hellwig
2019-10-15 20:43     ` Andrew Morton
2019-10-15 11:35 ` Project idea: Swap to " Matthew Wilcox
2019-10-15 13:27   ` Theodore Y. Ts'o
2019-10-15 13:48   ` Hannes Reinecke [this message]
2019-10-15 14:50     ` Christopher Lameter
2019-10-15 15:09     ` Matthew Wilcox
2019-10-15 15:22       ` Hannes Reinecke

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