Message-ID: <55E164C6.3000702@linux.vnet.ibm.com>
Date: Sat, 29 Aug 2015 13:22:38 +0530
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Organization: IBM
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To: Eric Dumazet <eric.dumazet@gmail.com>
CC: David Miller <davem@davemloft.net>, 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
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> <20150828.112413.424099339331017970.davem@davemloft.net> <20150829025715.GA5546@linux.vnet.ibm.com> <1440818791.8932.128.camel@edumazet-glaptop2.roam.corp.google.com>
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On 08/29/2015 08:56 AM, Eric Dumazet wrote:
> On Sat, 2015-08-29 at 08:27 +0530, Raghavendra K T wrote:
>>
>>   	/* Use put_unaligned() because stats may not be aligned for u64. */
>>   	put_unaligned(items, &stats[0]);
>
>
>>   	for (i = 1; i < items; i++)
>> -		put_unaligned(snmp_fold_field64(mib, i, syncpoff), &stats[i]);
>> +		put_unaligned(buff[i], &stats[i]);
>>
>
> I believe Joe suggested following code instead :
>
> buff[0] = items;
> memcpy(stats, buff, items * sizeof(u64));

Thanks. Sure, will use this.

(I missed that. I thought that it was applicable only when we have
aligned data,and for power, put_aunaligned was not a nop unlike intel).

>
> Also please move buff[] array into __snmp6_fill_stats64() to make it
> clear it is used in a 'leaf' function.

Correct.

>
> (even if calling memcpy()/memset() makes it not a leaf function)
>

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