On 08/26/2015 04:26 PM, Dave Young wrote:
On 08/26/15 at 04:18pm, "Zhou, Wenjian/周文剑" wrote:
> Hello Dave,
>
> On 08/26/2015 03:59 PM, Dave Young wrote:
>> Hi,
>>
>> 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(a)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!"
>>
>> It is better to do this in makedumpfile source code instead of adding
>> these warnings specific for num-threads here.
>>
>
> I have one more question.
> Since multi-thread feature is associated with nr_cpus, should we do something here?
Hmm, adding it in makedumpfile will be too late for warning users. But I do not like
adding these stuff in distribution script, user should know the limitation if he
choose the thread number. How about moving it to makedumpfile --help to describe
the problem just around the num_threads option.
Whatever, we should not introduce nr_cpus in makedumpfile --help.
I noticed a discussion between Vivek and Hatayama.
(You can refer to
https://lists.fedoraproject.org/pipermail/kexec/2014-March/000687.html)
I think finishing that patch may help.
I will post the patch later.
Please give me some comments on the later patch.
--
Thanks
Zhou