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authorDaniel Borkmann <daniel@iogearbox.net>2015-02-25 18:31:53 +0300
committerDavid S. Miller <davem@davemloft.net>2015-02-28 00:06:02 +0300
commit8331de75cb13fc907ceba78e698c42150e61dda9 (patch)
tree5732e31d9694fa924ee1460b363801bcbfce2304 /net/tipc
parent0d79a493e507437a2135e5ac1a447d4d503488d8 (diff)
downloadlinux-8331de75cb13fc907ceba78e698c42150e61dda9.tar.xz
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 <johunt@akamai.com> Fixes: c0c09bfdc415 ("rhashtable: avoid unnecessary wakeup for worker queue") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Ying Xue <ying.xue@windriver.com> Cc: Josh Hunt <johunt@akamai.com> Acked-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
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