From: Dan Streetman <ddstreet@ieee.org>
To: Weijie Yang <weijie.yang.kh@gmail.com>
Cc: Seth Jennings <sjennings@variantweb.net>,
linux-mm@kvack.org, linux-kernel <linux-kernel@vger.kernel.org>,
Bob Liu <bob.liu@oracle.com>, Minchan Kim <minchan@kernel.org>,
Weijie Yang <weijie.yang@samsung.com>
Subject: Re: [PATCH v3] mm/zswap: change zswap to writethrough cache
Date: Sat, 23 Nov 2013 15:35:35 -0500 [thread overview]
Message-ID: <CALZtONByDcL+yd3rMfFmrW_a2dV3ZV8XKiWcxba-oWTWeGNVVQ@mail.gmail.com> (raw)
In-Reply-To: <CAL1ERfNWXFmKFbVf2H1G7A=rVfxh+0ScN_yn_YcH=VsUr3bVjg@mail.gmail.com>
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?
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prev parent reply other threads:[~2013-11-23 20:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 19:49 [PATCH v2] " Dan Streetman
2013-11-21 0:42 ` Bob Liu
2013-11-21 3:50 ` Weijie Yang
2013-11-21 23:00 ` Dan Streetman
2013-11-21 22:38 ` Dan Streetman
2013-11-22 17:29 ` Seth Jennings
2013-11-22 18:07 ` Dan Streetman
2013-11-25 18:00 ` Seth Jennings
2013-11-27 1:28 ` Dan Streetman
2013-12-11 9:02 ` Bob Liu
2013-12-13 2:58 ` Dan Streetman
2013-11-22 22:10 ` [PATCH v3] " Dan Streetman
2013-11-23 2:37 ` Weijie Yang
2013-11-23 20:35 ` Dan Streetman [this message]
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