Commit e6308be85afee685347fa3440bed10faaa5d6c1a
Committed by
David S. Miller
David S. Miller
1 parent
87bf9c97b4
Exists in
master
and in
7 other branches
[IPV4]: fib_trie root-node expansion
The patch below introduces special thresholds to keep root node in the trie
large. This gives a flatter tree at the cost of a modest memory increase.
Overall it seems to be gain and this was also proposed by one the authors
of the paper in recent a seminar.
Main table after loading 123 k routes.
Aver depth: 3.30
Max depth: 9
Root-node size 12 bits
Total size: 4044 kB
With the patch:
Aver depth: 2.78
Max depth: 8
Root-node size 15 bits
Total size: 4150 kB
An increase of 8-10% was seen in forwading performance for an rDoS attack.
Signed-off-by: Robert Olsson <robert.olsson@its.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>
Showing 1 changed file with 21 additions and 2 deletions Side-by-side Diff
net/ipv4/fib_trie.c
| ... | ... | @@ -286,6 +286,8 @@ |
| 286 | 286 | |
| 287 | 287 | static int halve_threshold = 25; |
| 288 | 288 | static int inflate_threshold = 50; |
| 289 | +static int halve_threshold_root = 15; | |
| 290 | +static int inflate_threshold_root = 25; | |
| 289 | 291 | |
| 290 | 292 | |
| 291 | 293 | static void __alias_free_mem(struct rcu_head *head) |
| ... | ... | @@ -449,6 +451,8 @@ |
| 449 | 451 | int i; |
| 450 | 452 | int err = 0; |
| 451 | 453 | struct tnode *old_tn; |
| 454 | + int inflate_threshold_use; | |
| 455 | + int halve_threshold_use; | |
| 452 | 456 | |
| 453 | 457 | if (!tn) |
| 454 | 458 | return NULL; |
| 455 | 459 | |
| ... | ... | @@ -541,10 +545,17 @@ |
| 541 | 545 | |
| 542 | 546 | check_tnode(tn); |
| 543 | 547 | |
| 548 | + /* Keep root node larger */ | |
| 549 | + | |
| 550 | + if(!tn->parent) | |
| 551 | + inflate_threshold_use = inflate_threshold_root; | |
| 552 | + else | |
| 553 | + inflate_threshold_use = inflate_threshold; | |
| 554 | + | |
| 544 | 555 | err = 0; |
| 545 | 556 | while ((tn->full_children > 0 && |
| 546 | 557 | 50 * (tn->full_children + tnode_child_length(tn) - tn->empty_children) >= |
| 547 | - inflate_threshold * tnode_child_length(tn))) { | |
| 558 | + inflate_threshold_use * tnode_child_length(tn))) { | |
| 548 | 559 | |
| 549 | 560 | old_tn = tn; |
| 550 | 561 | tn = inflate(t, tn); |
| 551 | 562 | |
| ... | ... | @@ -564,10 +575,18 @@ |
| 564 | 575 | * node is above threshold. |
| 565 | 576 | */ |
| 566 | 577 | |
| 578 | + | |
| 579 | + /* Keep root node larger */ | |
| 580 | + | |
| 581 | + if(!tn->parent) | |
| 582 | + halve_threshold_use = halve_threshold_root; | |
| 583 | + else | |
| 584 | + halve_threshold_use = halve_threshold; | |
| 585 | + | |
| 567 | 586 | err = 0; |
| 568 | 587 | while (tn->bits > 1 && |
| 569 | 588 | 100 * (tnode_child_length(tn) - tn->empty_children) < |
| 570 | - halve_threshold * tnode_child_length(tn)) { | |
| 589 | + halve_threshold_use * tnode_child_length(tn)) { | |
| 571 | 590 | |
| 572 | 591 | old_tn = tn; |
| 573 | 592 | tn = halve(t, tn); |