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netfilter: ip_tables: unfold two critical loops in ip_packet_match()

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While doing oprofile tests I noticed two loops are not properly unrolled by gcc

Using a hand coded unrolled loop provides nice speedup : ipt_do_table
credited of 2.52 % of cpu instead of 3.29 % in tbench.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Eric Dumazet 2009-02-20 11:03:33 +01:00 committed by Patrick McHardy
parent 268cb38e18
commit 08361aa807
1 changed files with 21 additions and 12 deletions
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33
net/ipv4/netfilter/ip_tables.c
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@ -74,6 +74,25 @@ do { \
Hence the start of any table is given by get_table() below. */
static unsigned long ifname_compare(const char *_a, const char *_b,
const unsigned char *_mask)
{
const unsigned long *a = (const unsigned long *)_a;
const unsigned long *b = (const unsigned long *)_b;
const unsigned long *mask = (const unsigned long *)_mask;
unsigned long ret;
ret = (a[0] ^ b[0]) & mask[0];
if (IFNAMSIZ > sizeof(unsigned long))
ret |= (a[1] ^ b[1]) & mask[1];
if (IFNAMSIZ > 2 * sizeof(unsigned long))
ret |= (a[2] ^ b[2]) & mask[2];
if (IFNAMSIZ > 3 * sizeof(unsigned long))
ret |= (a[3] ^ b[3]) & mask[3];
BUILD_BUG_ON(IFNAMSIZ > 4 * sizeof(unsigned long));
return ret;
}
/* Returns whether matches rule or not. */
/* Performance critical - called for every packet */
static inline bool
@ -83,7 +102,6 @@ ip_packet_match(const struct iphdr *ip,
const struct ipt_ip *ipinfo,
int isfrag)
{
size_t i;
unsigned long ret;
#define FWINV(bool, invflg) ((bool) ^ !!(ipinfo->invflags & (invflg)))
@ -103,12 +121,7 @@ ip_packet_match(const struct iphdr *ip,
return false;
}
/* Look for ifname matches; this should unroll nicely. */
for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
ret |= (((const unsigned long *)indev)[i]
^ ((const unsigned long *)ipinfo->iniface)[i])
& ((const unsigned long *)ipinfo->iniface_mask)[i];
}
ret = ifname_compare(indev, ipinfo->iniface, ipinfo->iniface_mask);
if (FWINV(ret != 0, IPT_INV_VIA_IN)) {
dprintf("VIA in mismatch (%s vs %s).%s\n",
@ -117,11 +130,7 @@ ip_packet_match(const struct iphdr *ip,
return false;
}
for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
ret |= (((const unsigned long *)outdev)[i]
^ ((const unsigned long *)ipinfo->outiface)[i])
& ((const unsigned long *)ipinfo->outiface_mask)[i];
}
ret = ifname_compare(outdev, ipinfo->outiface, ipinfo->outiface_mask);
if (FWINV(ret != 0, IPT_INV_VIA_OUT)) {
dprintf("VIA out mismatch (%s vs %s).%s\n",