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authorEric Dumazet <dada1@cosmosbay.com>2007-11-07 05:40:20 -0500
committerDavid S. Miller <davem@sunset.davemloft.net>2007-11-07 07:15:11 -0500
commit230140cffa7feae90ad50bf259db1fa07674f3a7 (patch)
tree815472add31606423a508a17806b7884f0ab3e2e /net/ipv4/tcp.c
parentefac52762b1e3fe3035d29e82d8ee1aebc45e4a7 (diff)
[INET]: Remove per bucket rwlock in tcp/dccp ehash table.
As done two years ago on IP route cache table (commit 22c047ccbc68fa8f3fa57f0e8f906479a062c426) , we can avoid using one lock per hash bucket for the huge TCP/DCCP hash tables. On a typical x86_64 platform, this saves about 2MB or 4MB of ram, for litle performance differences. (we hit a different cache line for the rwlock, but then the bucket cache line have a better sharing factor among cpus, since we dirty it less often). For netstat or ss commands that want a full scan of hash table, we perform fewer memory accesses. Using a 'small' table of hashed rwlocks should be more than enough to provide correct SMP concurrency between different buckets, without using too much memory. Sizing of this table depends on num_possible_cpus() and various CONFIG settings. This patch provides some locking abstraction that may ease a future work using a different model for TCP/DCCP table. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp.c')
-rw-r--r--net/ipv4/tcp.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c64072bb504b..8e65182f7af1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2456,11 +2456,11 @@ void __init tcp_init(void)
2456 thash_entries ? 0 : 512 * 1024); 2456 thash_entries ? 0 : 512 * 1024);
2457 tcp_hashinfo.ehash_size = 1 << tcp_hashinfo.ehash_size; 2457 tcp_hashinfo.ehash_size = 1 << tcp_hashinfo.ehash_size;
2458 for (i = 0; i < tcp_hashinfo.ehash_size; i++) { 2458 for (i = 0; i < tcp_hashinfo.ehash_size; i++) {
2459 rwlock_init(&tcp_hashinfo.ehash[i].lock);
2460 INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].chain); 2459 INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].chain);
2461 INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].twchain); 2460 INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].twchain);
2462 } 2461 }
2463 2462 if (inet_ehash_locks_alloc(&tcp_hashinfo))
2463 panic("TCP: failed to alloc ehash_locks");
2464 tcp_hashinfo.bhash = 2464 tcp_hashinfo.bhash =
2465 alloc_large_system_hash("TCP bind", 2465 alloc_large_system_hash("TCP bind",
2466 sizeof(struct inet_bind_hashbucket), 2466 sizeof(struct inet_bind_hashbucket),