From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: Dmitry Safonov <dima@arista.com>, linux-kernel@vger.kernel.org
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
David Ahern <dsahern@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
Ido Schimmel <idosch@mellanox.com>,
netdev@vger.kernel.org
Subject: Re: [RFC 3/4] net/fib: Check budget before should_{inflate,halve}()
Date: Mon, 01 Apr 2019 11:20:26 -0700 [thread overview]
Message-ID: <cbbdf9e2cf6a64e749ec889cc946e2a10c793ba2.camel@linux.intel.com> (raw)
In-Reply-To: <20190326153026.24493-4-dima@arista.com>
On Tue, 2019-03-26 at 15:30 +0000, Dmitry Safonov wrote:
> Those functions are compute-costly, if we're out of budget - better
> omit additional computations.
>
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> ---
> net/ipv4/fib_trie.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index d90cf9dfd443..2ce2739e7693 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -868,7 +868,7 @@ static struct key_vector *resize(struct trie *t, struct key_vector *tn,
> /* Double as long as the resulting node has a number of
> * nonempty nodes that are above the threshold.
> */
> - while (should_inflate(tp, tn) && *budget) {
> + while (*budget && should_inflate(tp, tn)) {
> tp = inflate(t, tn, budget);
> if (!tp) {
> #ifdef CONFIG_IP_FIB_TRIE_STATS
> @@ -894,7 +894,7 @@ static struct key_vector *resize(struct trie *t, struct key_vector *tn,
> /* Halve as long as the number of empty children in this
> * node is above threshold.
> */
> - while (should_halve(tp, tn) && *budget) {
> + while (*budget && should_halve(tp, tn)) {
> tp = halve(t, tn, budget);
> if (!tp) {
> #ifdef CONFIG_IP_FIB_TRIE_STATS
Based on my comments in the other patches I would say this is a bad
idea.
Really the budget should allow at least 1 pass through the trie to
attempt to either inflate or deflate the node and all children. This
logic is optimizing for the case where *budget is 0 and that should not
occur that often.
next prev parent reply other threads:[~2019-04-01 18:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 15:30 [RFC 0/4] net/fib: Speed up trie rebalancing for full view Dmitry Safonov
2019-03-26 15:30 ` [RFC 1/4] net/ipv4/fib: Remove run-time check in tnode_alloc() Dmitry Safonov
2019-04-01 15:40 ` Alexander Duyck
2019-04-01 15:55 ` Dmitry Safonov
2019-04-01 17:50 ` Alexander Duyck
2019-04-04 16:33 ` Dmitry Safonov
2019-03-26 15:30 ` [RFC 2/4] net/fib: Provide fib_balance_budget sysctl Dmitry Safonov
2019-04-01 18:09 ` Alexander Duyck
2019-04-04 18:31 ` Dmitry Safonov
2019-03-26 15:30 ` [RFC 3/4] net/fib: Check budget before should_{inflate,halve}() Dmitry Safonov
2019-04-01 18:20 ` Alexander Duyck [this message]
2019-03-26 15:30 ` [RFC 4/4] net/ipv4/fib: Don't synchronise_rcu() every 512Kb Dmitry Safonov
2019-03-26 15:39 ` David Ahern
2019-03-26 17:15 ` Dmitry Safonov
2019-03-26 17:57 ` David Ahern
2019-03-26 18:17 ` Dmitry Safonov
2019-03-26 23:14 ` Dmitry Safonov
2019-03-27 3:33 ` Paul E. McKenney
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