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Message-ID: <cbbdf9e2cf6a64e749ec889cc946e2a10c793ba2.camel@linux.intel.com> Date: Mon, 01 Apr 2019 11:20:26 -0700 From: Alexander Duyck <alexander.h.duyck@...ux.intel.com> To: Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>, David Ahern <dsahern@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Ido Schimmel <idosch@...lanox.com>, netdev@...r.kernel.org Subject: Re: [RFC 3/4] net/fib: Check budget before should_{inflate,halve}() 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@...sta.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.
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