Date: Fri, 28 Aug 2015 11:24:13 -0700 (PDT)
Message-Id: <20150828.112413.424099339331017970.davem@davemloft.net>
To: raghavendra.kt@linux.vnet.ibm.com
Cc: edumazet@google.com, kuznet@ms2.inr.ac.ru, jmorris@namei.org,
        yoshfuji@linux-ipv6.org, kaber@trash.net, jiri@resnulli.us,
        hannes@stressinduktion.org, tom@herbertland.com, azhou@nicira.com,
        ebiederm@xmission.com, ipm@chirality.org.uk, nicolas.dichtel@6wind.com,
        serge.hallyn@canonical.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, anton@au1.ibm.com,
        nacc@linux.vnet.ibm.com, srikar@linux.vnet.ibm.com
Subject: Re: [PATCH RFC V2 2/2] net: Optimize snmp stat aggregation by
 walking all the percpu data at once
From: David Miller <davem@davemloft.net>
In-Reply-To: <55E00238.10909@linux.vnet.ibm.com>
References: <1440610653-14210-3-git-send-email-raghavendra.kt@linux.vnet.ibm.com>
	<20150827.113823.214019265460582055.davem@davemloft.net>
	<55E00238.10909@linux.vnet.ibm.com>
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From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Date: Fri, 28 Aug 2015 12:09:52 +0530

> On 08/28/2015 12:08 AM, David Miller wrote:
>> From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
>> Date: Wed, 26 Aug 2015 23:07:33 +0530
>>
>>> @@ -4641,10 +4647,12 @@ static inline void __snmp6_fill_stats64(u64
>>> *stats, void __percpu *mib,
>>>   static void snmp6_fill_stats(u64 *stats, struct inet6_dev *idev, int
>>>   attrtype,
>>>   			     int bytes)
>>>   {
>>> +	u64 buff[IPSTATS_MIB_MAX] = {0,};
>>> +
 ...
> hope you wanted to know the overhead than to change the current
> patch. please let me know..

I want you to change that variable initializer to an explicit memset().

The compiler is emitting a memset() or similar _anyways_.

Not because it will have any impact at all upon performance, but because
of how it looks to people trying to read and understand the code.
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