diff options
author | Eric Dumazet <dada1@cosmosbay.com> | 2008-11-16 19:46:36 -0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2008-11-16 19:46:36 -0800 |
commit | 5635c10d976716ef47ae441998aeae144c7e7387 (patch) | |
tree | 03cb08b634fba283bbde42ea290c92048045d2fd /net | |
parent | 536533e69e3e4a9f0174509813f8df28970d6ebe (diff) |
net: make sure struct dst_entry refcount is aligned on 64 bytes
As found in the past (commit f1dd9c379cac7d5a76259e7dffcd5f8edc697d17
[NET]: Fix tbench regression in 2.6.25-rc1), it is really
important that struct dst_entry refcount is aligned on a cache line.
We cannot use __atribute((aligned)), so manually pad the structure
for 32 and 64 bit arches.
for 32bit : offsetof(truct dst_entry, __refcnt) is 0x80
for 64bit : offsetof(truct dst_entry, __refcnt) is 0xc0
As it is not possible to guess at compile time cache line size,
we use a generic value of 64 bytes, that satisfies many current arches.
(Using 128 bytes alignment on 64bit arches would waste 64 bytes)
Add a BUILD_BUG_ON to catch future updates to "struct dst_entry" dont
break this alignment.
"tbench 8" is 4.4 % faster on a dual quad core (HP BL460c G1), Intel E5450 @3.00GHz
(2350 MB/s instead of 2250 MB/s)
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
0 files changed, 0 insertions, 0 deletions