>>In /net/netfilter/nfnetlink_queue.c every call of nfqnl_build_packet_message()
>>make series of call nla_total_size() for 'size' calculations.
>>I think 'size' is constant value for kernel build and may be define static
>>variable for this ?
>>
>> size = NLMSG_SPACE(sizeof(struct nfgenmsg))
>> + nla_total_size(sizeof(struct nfqnl_msg_packet_hdr))
>> + nla_total_size(sizeof(u_int32_t)) /* ifindex */
>> + nla_total_size(sizeof(u_int32_t)) /* ifindex */
JE> The compiler will optimize it out.
Okey. It's easy to test.
=========== 1.c =======================
#include <stdlib.h>
#include <stdio.h>
#define NLA_ALIGNTO 4
#define NLA_ALIGN(len) (((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1))
#define NLA_HDRLEN 30
static inline int nla_attr_size(int payload)
{
return NLA_HDRLEN + payload;
}
static inline int nla_total_size(int payload)
{
return NLA_ALIGN(nla_attr_size(payload));
}
size_t nfqnl_build_packet_message(int len) {
size_t size;
size = nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)); /* mark */
return size;
};
int main () {
long i;
size_t ret;
int r = 0;
for (i = 0; i < 100000000; i++) {
r = rand();
printf("%d",r);
ret = nfqnl_build_packet_message(r);
};
}
======================== end of 1.c ========================
And other case
===================== 2.c =============================
#include <stdlib.h>
#include <stdio.h>
#define NLA_ALIGNTO 4
#define NLA_ALIGN(len) (((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1))
#define NLA_HDRLEN 30
static inline int nla_attr_size(int payload)
{
return NLA_HDRLEN + payload;
}
static inline int nla_total_size(int payload)
{
return NLA_ALIGN(nla_attr_size(payload));
}
size_t size_global = 0; ///// GLOBAL PRECALCULATED VALUE
size_t nfqnl_build_packet_message(int len) {
size_t size;
size = size_global;
return size;
};
int main () {
long i;
size_t ret;
//////// calculations here
size_global = nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)) /* ifindex */
+ nla_total_size(sizeof(u_int32_t)); /* mark */
int r = 0;
for (i = 0; i < 100000000; i++) {
r = rand();
printf("%d",r);
ret = nfqnl_build_packet_message(r);
};
}
===========================================
And some tests....
root@bill:/src/1# gcc 1.c
root@bill:/src/1# time ./a.out > /dev/null
real 0m20.253s
user 0m20.209s
sys 0m0.041s
root@bill:/src/1# gcc 2.c
root@bill:/src/1# time ./a.out > /dev/null
real 0m17.030s
user 0m16.988s
sys 0m0.040s
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Kuzin Andrey - kuzinandrey@xxxxxxxxx
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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