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netfilter: ip_tables: unfold two critical loops in ip_packet_match()
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>
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@ -74,6 +74,25 @@ do { \
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Hence the start of any table is given by get_table() below. */
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static unsigned long ifname_compare(const char *_a, const char *_b,
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const unsigned char *_mask)
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{
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const unsigned long *a = (const unsigned long *)_a;
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const unsigned long *b = (const unsigned long *)_b;
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const unsigned long *mask = (const unsigned long *)_mask;
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unsigned long ret;
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ret = (a[0] ^ b[0]) & mask[0];
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if (IFNAMSIZ > sizeof(unsigned long))
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ret |= (a[1] ^ b[1]) & mask[1];
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if (IFNAMSIZ > 2 * sizeof(unsigned long))
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ret |= (a[2] ^ b[2]) & mask[2];
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if (IFNAMSIZ > 3 * sizeof(unsigned long))
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ret |= (a[3] ^ b[3]) & mask[3];
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BUILD_BUG_ON(IFNAMSIZ > 4 * sizeof(unsigned long));
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return ret;
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}
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/* Returns whether matches rule or not. */
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/* Performance critical - called for every packet */
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static inline bool
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@ -83,7 +102,6 @@ ip_packet_match(const struct iphdr *ip,
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const struct ipt_ip *ipinfo,
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int isfrag)
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{
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size_t i;
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unsigned long ret;
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#define FWINV(bool, invflg) ((bool) ^ !!(ipinfo->invflags & (invflg)))
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@ -103,12 +121,7 @@ ip_packet_match(const struct iphdr *ip,
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return false;
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}
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/* Look for ifname matches; this should unroll nicely. */
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for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
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ret |= (((const unsigned long *)indev)[i]
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^ ((const unsigned long *)ipinfo->iniface)[i])
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& ((const unsigned long *)ipinfo->iniface_mask)[i];
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}
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ret = ifname_compare(indev, ipinfo->iniface, ipinfo->iniface_mask);
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if (FWINV(ret != 0, IPT_INV_VIA_IN)) {
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dprintf("VIA in mismatch (%s vs %s).%s\n",
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@ -117,11 +130,7 @@ ip_packet_match(const struct iphdr *ip,
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return false;
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}
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for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
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ret |= (((const unsigned long *)outdev)[i]
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^ ((const unsigned long *)ipinfo->outiface)[i])
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& ((const unsigned long *)ipinfo->outiface_mask)[i];
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}
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ret = ifname_compare(outdev, ipinfo->outiface, ipinfo->outiface_mask);
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if (FWINV(ret != 0, IPT_INV_VIA_OUT)) {
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dprintf("VIA out mismatch (%s vs %s).%s\n",
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