[PATCH v2] Add checking num-threads of makedumpfile

[Minfei Huang]

Hi. Wenjian.

Thougt deeply about this patch, I have following concerns.

Without this patch, do you have any testing about the performance
degradation, if num_threads is larger than real cpu number?

Is it proper to do the checking in kdumpctl, since kdump takes more
care of setuping 2nd kernel, not the blendings of makedumpfile.

Thanks
Minfei

On 08/25/15 at 04:43pm, Zhou Wenjian wrote:
> A new feature that doing compressing and writing by multi-threads
> has been added in makedumpfile. The thread num is specified by
> "--num-threads NUM". According to its implementation, there will
> be performance degradation if the threads are more than cpus.
> So we should check it.
> 
> Signed-off-by: Zhou wenjian <zhouwj-fnst at cn.fujitsu.com>
> ---
>  kdumpctl |   15 +++++++++++++++
>  1 files changed, 15 insertions(+), 0 deletions(-)
> 
> diff --git a/kdumpctl b/kdumpctl
> index b504734..fd2abe4 100755
> --- a/kdumpctl
> +++ b/kdumpctl
> @@ -259,6 +259,21 @@ check_config()
>  		esac
>  	done < $KDUMP_CONFIG_FILE
>  
> +	grep "^core_collector.*makedumpfile" $KDUMP_CONFIG_FILE | grep -q "num-threads"
> +	if [ $? -eq 0 ];then
> +		local nr_cpus=1
> +		local num_threads=0
> +		local core_collector=`grep "^core_collector" $KDUMP_CONFIG_FILE`
> +
> +		num_threads=`echo ${core_collector#*--num-threads} | awk '{print $1}'`
> +		nr_cpus=`echo ${KDUMP_COMMANDLINE_APPEND#*nr_cpus=} | awk '{print $1}'`
> +
> +		if [ $num_threads -ge $nr_cpus ];then
> +			echo "The num_threads:$num_threads(specified in /etc/kdump.conf) should be less than nr_cpus:$nr_cpus(specified in /etc/sysconfig/kdump)"
> +			echo "or makedumpfile may have bad performance!"
> +		fi
> +	fi
> +
>  	check_fence_kdump_config || return 1
>  
>  	return 0
> -- 
> 1.7.1
> 
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