[dm-devel] dm-block-manager unused variable

lilofile lilofile at aliyun.com
Mon Nov 3 05:57:51 UTC 2014

in  file dm-block-manager.c,  in function dm_block_manager_create(),the variable cache_size unused? Any design considerations?

发件人:Mike Snitzer <snitzer at redhat.com>
发送时间:2014年11月2日(星期日) 02:46
收件人:lilofile <lilofile at aliyun.com>
抄 送:dm-devel <dm-devel at redhat.com>
主 题:Re: [dm-devel] dm-thin  COMMIT_PERIOD problem

On Sat, Nov 01 2014 at 10:40am -0400,
lilofile <lilofile at aliyun.com> wrote:

> In dm-thin.c,COMMIT_PERIOD is set HZ, I think this value has a  impact on system impact,too frequent commit will reduce the write performance of the system?
> other method which it is submitted by  the total size of dirty data   is feasible?

It only issues IO if changes have occured.  It isn't writing to disk
every second unless changes need to get to disk anyway.

(There was a bug where it _did_ write the metadata superblock every
second even when it wasn't needed.. since fixed with this commit:
http://git.kernel.org/linus/4d1662a30 )

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