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author | Daniel Borkmann <daniel@iogearbox.net> | 2015-02-25 16:31:53 +0100 |
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committer | David S. Miller <davem@davemloft.net> | 2015-02-27 16:06:02 -0500 |
commit | 8331de75cb13fc907ceba78e698c42150e61dda9 (patch) | |
tree | 5732e31d9694fa924ee1460b363801bcbfce2304 /net/netlink | |
parent | 0d79a493e507437a2135e5ac1a447d4d503488d8 (diff) | |
download | linux-8331de75cb13fc907ceba78e698c42150e61dda9.tar.bz2 |
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>
Diffstat (limited to 'net/netlink')
0 files changed, 0 insertions, 0 deletions