sch_dsmark: improve memory locality

Memory placement in sch_dsmark is silly : Better place mask/value
in the same cache line.

Also, we can embed small arrays in the first cache line and
remove a potential cache miss.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index c4d45fd8c551ef5b2c42910459b06c35667590ae..f357f34d02d2a5e9f4ead0ebe77ec44dca79f89a 100644 (file)
--- a/net/sched/sch_dsmark.c
+++ b/net/sched/sch_dsmark.c
@@ -35,14 +35,20 @@
 
 #define NO_DEFAULT_INDEX       (1 << 16)
 
+struct mask_value {
+       u8                      mask;
+       u8                      value;
+};
+
 struct dsmark_qdisc_data {
        struct Qdisc            *q;
        struct tcf_proto __rcu  *filter_list;
-       u8                      *mask;  /* "owns" the array */
-       u8                      *value;
+       struct mask_value       *mv;
        u16                     indices;
+       u8                      set_tc_index;
        u32                     default_index;  /* index range is 0...0xffff */
-       int                     set_tc_index;
+#define DSMARK_EMBEDDED_SZ     16
+       struct mask_value       embedded[DSMARK_EMBEDDED_SZ];
 };
 
 static inline int dsmark_valid_index(struct dsmark_qdisc_data *p, u16 index)
@@ -116,7 +122,6 @@ static int dsmark_change(struct Qdisc *sch, u32 classid, u32 parent,
        struct nlattr *opt = tca[TCA_OPTIONS];
        struct nlattr *tb[TCA_DSMARK_MAX + 1];
        int err = -EINVAL;
-       u8 mask = 0;
 
        pr_debug("%s(sch %p,[qdisc %p],classid %x,parent %x), arg 0x%lx\n",
                 __func__, sch, p, classid, parent, *arg);
@@ -133,14 +138,11 @@ static int dsmark_change(struct Qdisc *sch, u32 classid, u32 parent,
        if (err < 0)
                goto errout;
 
-       if (tb[TCA_DSMARK_MASK])
-               mask = nla_get_u8(tb[TCA_DSMARK_MASK]);
-
        if (tb[TCA_DSMARK_VALUE])
-               p->value[*arg - 1] = nla_get_u8(tb[TCA_DSMARK_VALUE]);
+               p->mv[*arg - 1].value = nla_get_u8(tb[TCA_DSMARK_VALUE]);
 
        if (tb[TCA_DSMARK_MASK])
-               p->mask[*arg - 1] = mask;
+               p->mv[*arg - 1].mask = nla_get_u8(tb[TCA_DSMARK_MASK]);
 
        err = 0;
 
@@ -155,8 +157,8 @@ static int dsmark_delete(struct Qdisc *sch, unsigned long arg)
        if (!dsmark_valid_index(p, arg))
                return -EINVAL;
 
-       p->mask[arg - 1] = 0xff;
-       p->value[arg - 1] = 0;
+       p->mv[arg - 1].mask = 0xff;
+       p->mv[arg - 1].value = 0;
 
        return 0;
 }
@@ -173,7 +175,7 @@ static void dsmark_walk(struct Qdisc *sch, struct qdisc_walker *walker)
                return;
 
        for (i = 0; i < p->indices; i++) {
-               if (p->mask[i] == 0xff && !p->value[i])
+               if (p->mv[i].mask == 0xff && !p->mv[i].value)
                        goto ignore;
                if (walker->count >= walker->skip) {
                        if (walker->fn(sch, i + 1, walker) < 0) {
@@ -291,12 +293,12 @@ static struct sk_buff *dsmark_dequeue(struct Qdisc *sch)
 
        switch (tc_skb_protocol(skb)) {
        case htons(ETH_P_IP):
-               ipv4_change_dsfield(ip_hdr(skb), p->mask[index],
-                                   p->value[index]);
+               ipv4_change_dsfield(ip_hdr(skb), p->mv[index].mask,
+                                   p->mv[index].value);
                        break;
        case htons(ETH_P_IPV6):
-               ipv6_change_dsfield(ipv6_hdr(skb), p->mask[index],
-                                   p->value[index]);
+               ipv6_change_dsfield(ipv6_hdr(skb), p->mv[index].mask,
+                                   p->mv[index].value);
                        break;
        default:
                /*
@@ -304,7 +306,7 @@ static struct sk_buff *dsmark_dequeue(struct Qdisc *sch)
                 * This way, we can send non-IP traffic through dsmark
                 * and don't need yet another qdisc as a bypass.
                 */
-               if (p->mask[index] != 0xff || p->value[index])
+               if (p->mv[index].mask != 0xff || p->mv[index].value)
                        pr_warn("%s: unsupported protocol %d\n",
                                __func__, ntohs(tc_skb_protocol(skb)));
                break;
@@ -346,7 +348,7 @@ static int dsmark_init(struct Qdisc *sch, struct nlattr *opt)
        int err = -EINVAL;
        u32 default_index = NO_DEFAULT_INDEX;
        u16 indices;
-       u8 *mask;
+       int i;
 
        pr_debug("%s(sch %p,[qdisc %p],opt %p)\n", __func__, sch, p, opt);
 
@@ -366,18 +368,18 @@ static int dsmark_init(struct Qdisc *sch, struct nlattr *opt)
        if (tb[TCA_DSMARK_DEFAULT_INDEX])
                default_index = nla_get_u16(tb[TCA_DSMARK_DEFAULT_INDEX]);
 
-       mask = kmalloc(indices * 2, GFP_KERNEL);
-       if (mask == NULL) {
+       if (indices <= DSMARK_EMBEDDED_SZ)
+               p->mv = p->embedded;
+       else
+               p->mv = kmalloc_array(indices, sizeof(*p->mv), GFP_KERNEL);
+       if (!p->mv) {
                err = -ENOMEM;
                goto errout;
        }
-
-       p->mask = mask;
-       memset(p->mask, 0xff, indices);
-
-       p->value = p->mask + indices;
-       memset(p->value, 0, indices);
-
+       for (i = 0; i < indices; i++) {
+               p->mv[i].mask = 0xff;
+               p->mv[i].value = 0;
+       }
        p->indices = indices;
        p->default_index = default_index;
        p->set_tc_index = nla_get_flag(tb[TCA_DSMARK_SET_TC_INDEX]);
@@ -410,7 +412,8 @@ static void dsmark_destroy(struct Qdisc *sch)
 
        tcf_destroy_chain(&p->filter_list);
        qdisc_destroy(p->q);
-       kfree(p->mask);
+       if (p->mv != p->embedded)
+               kfree(p->mv);
 }
 
 static int dsmark_dump_class(struct Qdisc *sch, unsigned long cl,
@@ -430,8 +433,8 @@ static int dsmark_dump_class(struct Qdisc *sch, unsigned long cl,
        opts = nla_nest_start(skb, TCA_OPTIONS);
        if (opts == NULL)
                goto nla_put_failure;
-       if (nla_put_u8(skb, TCA_DSMARK_MASK, p->mask[cl - 1]) ||
-           nla_put_u8(skb, TCA_DSMARK_VALUE, p->value[cl - 1]))
+       if (nla_put_u8(skb, TCA_DSMARK_MASK, p->mv[cl - 1].mask) ||
+           nla_put_u8(skb, TCA_DSMARK_VALUE, p->mv[cl - 1].value))
                goto nla_put_failure;
 
        return nla_nest_end(skb, opts);