lkml.org 
[lkml]   [2013]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v3] mm/zswap: change zswap to writethrough cache
On Fri, Nov 22, 2013 at 9:37 PM, Weijie Yang <weijie.yang.kh@gmail.com> wrote:
> Hello Dan,
>
> On Sat, Nov 23, 2013 at 6:10 AM, Dan Streetman <ddstreet@ieee.org> wrote:
>> Currently, zswap is writeback cache; stored pages are not sent
>> to swap disk, and when zswap wants to evict old pages it must
>> first write them back to swap cache/disk manually. This avoids
>> swap out disk I/O up front, but only moves that disk I/O to
>> the writeback case (for pages that are evicted), and adds the
>> overhead of having to uncompress the evicted pages, and adds the
>> need for an additional free page (to store the uncompressed page)
>> at a time of likely high memory pressure. Additionally, being
>> writeback adds complexity to zswap by having to perform the
>> writeback on page eviction.
>>
>> This changes zswap to writethrough cache by enabling
>> frontswap_writethrough() before registering, so that any
>> successful page store will also be written to swap disk. All the
>> writeback code is removed since it is no longer needed, and the
>> only operation during a page eviction is now to remove the entry
>> from the tree and free it.
>
> I agree with Seth, It is not good to embedded device.
> May be we can find its place in others like server.
> I guess it is good to medium workload when swap io is not frequent.
>
> My suggestion is would you please make it configurable so that user
> can choice to use writethrough or writeback mode?
>

Having to support both significantly increases complexity and I think
would make further improvements more difficult. My opinion is the
writeback code should be removed. Is there anyone else who thinks
both should be available by a param?


\
 
 \ /
  Last update: 2013-11-23 22:01    [W:0.050 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site