diff options
| author |   Dave Barach <dave@barachs.net> | 2019-03-07 10:06:52 -0500 |
|---|---|---|
| committer |   Damjan Marion <dmarion@me.com> | 2019-03-07 19:39:28 +0000 |
| commit | 974931f162820bd4ba41a43cae9578171cf0e3d1 (patch) | |
| tree | 8025ada44b91bb3c2f863bc98e80894794e1fd3b | |
| parent | f7c1a70ba502c83d6e5813344c01edbdfbff6738 (diff) | |
Honor vnet_rewrite_data_t data_bytes == 0
Avoid the cache miss consequences of spraying [functionally harmless]
junk into un-prefetched rewrite space. As things stand, several tunnel
encap rewrites set rewrite data_bytes = 0, and take a performance hit
due to unwanted speculative copying.
Should be performance-neutral in speed-path cases, which won't execute
the added check.
Change-Id: Id83c0325e58c0f31631b4bae5a06457dfc7ed567
Signed-off-by: Dave Barach <dave@barachs.net>
| -rw-r--r-- | src/vnet/adj/rewrite.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/src/vnet/adj/rewrite.h b/src/vnet/adj/rewrite.h index 58d47e0c737..32781134ecc 100644 --- a/src/vnet/adj/rewrite.h +++ b/src/vnet/adj/rewrite.h @@ -189,7 +189,13 @@ _vnet_rewrite_one_header (vnet_rewrite_header_t * h0, clib_memcpy (d, s, sizeof (eh_copy_t)); return; } - + /* + * Stop now if the data_bytes field is zero, to avoid the cache + * miss consequences of spraying [functionally harmless] junk into + * un-prefetched rewrite space. + */ + if (PREDICT_FALSE (h0->data_bytes == 0)) + return; #define _(i) \ do { \ @@ -244,6 +250,14 @@ _vnet_rewrite_two_headers (vnet_rewrite_header_t * h0, return; } + /* + * Stop now if both rewrite data_bytes fields are zero, to avoid the cache + * miss consequences of spraying [functionally harmless] junk into + * un-prefetched rewrite space. + */ + if (PREDICT_FALSE (h0->data_bytes + h1->data_bytes == 0)) + return; + #define _(i) \ do { \ if (most_likely_size > ((i)-1)*sizeof (vnet_rewrite_data_t)) \ |