From: Wanpeng Li <liwanp@linux.vnet.ibm.com>
To: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Seth Jennings <sjenning@linux.vnet.ibm.com>,
Konrad Rzeszutek Wilk <konrad@darnok.org>,
Minchan Kim <minchan@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] zcache: zero-filled pages awareness
Date: Thu, 14 Mar 2013 07:35:37 +0800 [thread overview]
Message-ID: <20130313233537.GA7635@hacker.(null)> (raw)
In-Reply-To: <9a45f4be-a80c-434d-ae7f-f8faaea5e4d4@default>
On Wed, Mar 13, 2013 at 09:53:48AM -0700, Dan Magenheimer wrote:
>> From: Wanpeng Li [mailto:liwanp@linux.vnet.ibm.com]
>> Subject: [PATCH 2/4] zcache: zero-filled pages awareness
>>
>> Compression of zero-filled pages can unneccessarily cause internal
>> fragmentation, and thus waste memory. This special case can be
>> optimized.
>>
>> This patch captures zero-filled pages, and marks their corresponding
>> zcache backing page entry as zero-filled. Whenever such zero-filled
>> page is retrieved, we fill the page frame with zero.
>>
>> Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>> ---
>> drivers/staging/zcache/tmem.c | 4 +-
>> drivers/staging/zcache/tmem.h | 5 ++
>> drivers/staging/zcache/zcache-main.c | 87 ++++++++++++++++++++++++++++++----
>> 3 files changed, 85 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/staging/zcache/tmem.c b/drivers/staging/zcache/tmem.c
>> index a2b7e03..62468ea 100644
>> --- a/drivers/staging/zcache/tmem.c
>> +++ b/drivers/staging/zcache/tmem.c
>> @@ -597,7 +597,9 @@ int tmem_put(struct tmem_pool *pool, struct tmem_oid *oidp, uint32_t index,
>> if (unlikely(ret == -ENOMEM))
>> /* may have partially built objnode tree ("stump") */
>> goto delete_and_free;
>> - (*tmem_pamops.create_finish)(pampd, is_ephemeral(pool));
>> + if (pampd != (void *)ZERO_FILLED)
>> + (*tmem_pamops.create_finish)(pampd, is_ephemeral(pool));
>> +
>> goto out;
>>
>> delete_and_free:
>> diff --git a/drivers/staging/zcache/tmem.h b/drivers/staging/zcache/tmem.h
>> index adbe5a8..6719dbd 100644
>> --- a/drivers/staging/zcache/tmem.h
>> +++ b/drivers/staging/zcache/tmem.h
>> @@ -204,6 +204,11 @@ struct tmem_handle {
>> uint16_t client_id;
>> };
>>
>> +/*
>> + * mark pampd to special vaule in order that later
>> + * retrieve will identify zero-filled pages
>> + */
>> +#define ZERO_FILLED 0x2
>
>You can avoid changing tmem.[ch] entirely by moving this
>definition into zcache-main.c and by moving the check
>comparing pampd against ZERO_FILLED into zcache_pampd_create_finish()
>I think that would be cleaner...
Great point!
>
>If you change this and make the pageframe counter fix for PATCH 4/4,
>please add my ack for the next version:
>
Thanks Dan. :-)
Regards,
Wanpeng Li
>Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
>
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next prev parent reply other threads:[~2013-03-13 23:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <<1363158321-20790-1-git-send-email-liwanp@linux.vnet.ibm.com>
[not found] ` <<1363158321-20790-5-git-send-email-liwanp@linux.vnet.ibm.com>
2013-03-13 16:42 ` [PATCH 4/4] zcache: add pageframes count once compress zero-filled pages twice Dan Magenheimer
2013-03-14 0:20 ` Wanpeng Li
2013-03-14 0:20 ` Wanpeng Li
2013-03-14 16:10 ` Dan Magenheimer
2013-03-14 23:41 ` Wanpeng Li
2013-03-14 23:41 ` Wanpeng Li
[not found] ` <<1363158321-20790-3-git-send-email-liwanp@linux.vnet.ibm.com>
2013-03-13 16:53 ` [PATCH 2/4] zcache: zero-filled pages awareness Dan Magenheimer
2013-03-13 23:35 ` Wanpeng Li
2013-03-13 23:35 ` Wanpeng Li [this message]
2013-03-13 7:05 [PATCH 0/4] zcache: Support zero-filled pages more efficiently Wanpeng Li
2013-03-13 7:05 ` [PATCH 1/4] zcache: introduce zero-filled pages handler Wanpeng Li
2013-03-13 7:05 ` [PATCH 2/4] zcache: zero-filled pages awareness Wanpeng Li
2013-03-13 7:05 ` [PATCH 3/4] zcache: introduce zero-filled pages stat count Wanpeng Li
2013-03-13 7:05 ` [PATCH 4/4] zcache: add pageframes count once compress zero-filled pages twice Wanpeng Li
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