linux-kernel - Re: [dm-devel] The DM_BUFIO_HASH_BITS is defined as 20, any plan to make it flexible?

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Message-ID: <547FB83B.8080401@windriver.com>
Date:	Thu, 4 Dec 2014 09:26:19 +0800
From:	zhangxiao <xiao.zhang@...driver.com>
To:	device-mapper development <dm-devel@...hat.com>,
	<linux-raid@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<agk@...hat.com>
Subject: Re: [dm-devel] The DM_BUFIO_HASH_BITS is defined as 20, any plan
 to make it flexible?

On 2014年12月03日 22:19, Joe Thornber wrote:
> On Tue, Dec 02, 2014 at 09:00:17AM -0500, Mike Snitzer wrote:
>> On Tue, Dec 02 2014 at  3:43am -0500,
>> zhangxiao <xiao.zhang@...driver.com> wrote:
>>
>>> Hi Experts,
>>>
>>> See drivers/md/dm-bufio.c as below:
>>>    50 /*
>>>    51  * Buffer hash
>>>    52  */
>>>    53 #define DM_BUFIO_HASH_BITS      20
>>>    54 #define DM_BUFIO_HASH(block) \
>>>    55         ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
>>>    56          ((1 << DM_BUFIO_HASH_BITS) - 1))
>>> "drivers/md/dm-bufio.c" 1854L, 45375C
>>>
>>> DM_BUFIO_HASH_BITS was defined as 20 and it maybe not fit for some
>>> use case with limited resources. Do we have any plan to make it more
>>> flexible? Like module parameter or something else?
>>
>> No immediate plans.
>
> That hash table has been replaced with a red/black tree.
>
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-for-3.19&id=4e420c452b11edf9d510c8180ac66f529e5b6206
>
>
Great Thanks!

Best Regards
Xiao
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