From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by walking all the percpu data at once Date: Sat, 29 Aug 2015 22:55:40 +0530 Message-ID: <55E1EB14.5040205@linux.vnet.ibm.com> References: <1440839278-21928-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <1440839278-21928-3-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <1440858726.8932.149.camel@edumazet-glaptop2.roam.corp.google.com> <1440861684.3276.7.camel@perches.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , davem@davemloft.net, kuznet@ms2.inr.ac.ru, jmorris@namei.org, yoshfuji@linux-ipv6.org, kaber@trash.net, jiri@resnulli.us, edumazet@google.com, 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 To: Joe Perches Return-path: Received: from e23smtp01.au.ibm.com ([202.81.31.143]:54186 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752364AbbH2RYi (ORCPT ); Sat, 29 Aug 2015 13:24:38 -0400 Received: from /spool/local by e23smtp01.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 30 Aug 2015 03:24:36 +1000 In-Reply-To: <1440861684.3276.7.camel@perches.com> Sender: netdev-owner@vger.kernel.org List-ID: On 08/29/2015 08:51 PM, Joe Perches wrote: > On Sat, 2015-08-29 at 07:32 -0700, Eric Dumazet wrote: >> On Sat, 2015-08-29 at 14:37 +0530, Raghavendra K T wrote: >> >>> >>> static inline void __snmp6_fill_stats64(u64 *stats, void __percpu *mib, >>> - int items, int bytes, size_t syncpoff) >>> + int items, int bytes, size_t syncpoff) >>> { >>> - int i; >>> + int i, c; >>> int pad = bytes - sizeof(u64) * items; >>> + u64 buff[items]; >>> + >> >> One last comment : using variable length arrays is confusing for the >> reader, and sparse as well. >> >> $ make C=2 net/ipv6/addrconf.o >> ... >> CHECK net/ipv6/addrconf.c >> net/ipv6/addrconf.c:4733:18: warning: Variable length array is used. >> net/ipv6/addrconf.c:4737:25: error: cannot size expression >> >> >> I suggest you remove 'items' parameter and replace it by >> IPSTATS_MIB_MAX, as __snmp6_fill_stats64() is called exactly once. > > If you respin, I suggest: > > o remove "items" from the __snmp6_fill_stats64 arguments > and use IPSTATS_MIB_MAX in the function instead Yes, as also suggested by Eric. > o add braces around the for_each_possible_cpu loop > > for_each_possible_cpu(c) { > for (i = 1; i < items; i++) > buff[i] += snmp_get_cpu_field64(mib, c, i, syncpoff); > } > Sure. It makes it more readable. will respin V4 with these changes (+ memset 0 for pad which I realized).