From 8331de75cb13fc907ceba78e698c42150e61dda9 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 25 Feb 2015 16:31:53 +0100 Subject: [PATCH] rhashtable: unconditionally grow when max_shift is not specified While commit c0c09bfdc415 ("rhashtable: avoid unnecessary wakeup for worker queue") rightfully moved part of the decision making of whether we should expand or shrink from the expand/shrink functions themselves into insert/delete functions in order to avoid unnecessary worker wake-ups, it however introduced a regression by doing so. Before that change, if no max_shift was specified (= 0) on rhashtable initialization, rhashtable_expand() would just grow unconditionally and lets the available memory be the limiting factor. After that change, if no max_shift was specified, there would be _no_ expansion step at all. Given that netlink and tipc have a max_shift specified, it was not visible there, but Josh Hunt reported that if nft that starts out with a default element hint of 3 if not otherwise provided, would slow i.e. inserts down trememdously as it cannot grow larger to relax table occupancy. Given that the test case verifies shrinks/expands manually, we also must remove pointer to the helper functions to explicitly avoid parallel resizing on insertions/deletions. test_bucket_stats() and test_rht_lookup() could also be wrapped around rhashtable mutex to explicitly synchronize a walk from resizing, but I think that defeats the actual test case which intended to have explicit test steps, i.e. 1) inserts, 2) expands, 3) shrinks, 4) deletions, with object verification after each stage. Reported-by: Josh Hunt Fixes: c0c09bfdc415 ("rhashtable: avoid unnecessary wakeup for worker queue") Signed-off-by: Daniel Borkmann Cc: Ying Xue Cc: Josh Hunt Acked-by: Thomas Graf Signed-off-by: David S. Miller --- lib/rhashtable.c | 2 +- lib/test_rhashtable.c | 2 -- 2 files changed, 1 insertion(+), 3 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index e3a04e4b3ec5..bcf119bfdef4 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -251,7 +251,7 @@ bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size) { /* Expand table when exceeding 75% load */ return atomic_read(&ht->nelems) > (new_size / 4 * 3) && - (ht->p.max_shift && atomic_read(&ht->shift) < ht->p.max_shift); + (!ht->p.max_shift || atomic_read(&ht->shift) < ht->p.max_shift); } EXPORT_SYMBOL_GPL(rht_grow_above_75); diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c index 58b995323c44..f9e9d734446a 100644 --- a/lib/test_rhashtable.c +++ b/lib/test_rhashtable.c @@ -202,8 +202,6 @@ static int __init test_rht_init(void) .key_len = sizeof(int), .hashfn = jhash, .nulls_base = (3U << RHT_BASE_SHIFT), - .grow_decision = rht_grow_above_75, - .shrink_decision = rht_shrink_below_30, }; int err; -- 2.20.1