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Re: [PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by walking all the percpu data at once

From Eric Dumazet <eric.dumazet@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by walking all the percpu data at once
Date 2015-08-29 16:40 +0200
Message-ID <q2Pst-4AG-1@gated-at.bofh.it> (permalink)
References <ds889-8u2-7@gated-at.bofh.it> <q2Kj7-5Iz-13@gated-at.bofh.it> <q2Kj7-5Iz-11@gated-at.bofh.it>
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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.



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Thread

[PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by walking all the percpu data at once Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> - 2015-08-29 11:10 +0200
  Re: [PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by  walking all the percpu data at once Eric Dumazet <eric.dumazet@gmail.com> - 2015-08-29 16:40 +0200
    Re: [PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by  walking all the percpu data at once Joe Perches <joe@perches.com> - 2015-08-29 17:30 +0200
      Re: [PATCH RFC V3 2/2] net: Optimize snmp stat aggregation by walking  all the percpu data at once Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> - 2015-08-29 19:30 +0200

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