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vppinfra: fix corner-cases in bihash lookup

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In a case where one pounds on a single kvp in a KVP_AT_BUCKET_LEVEL
table, the code would sporadically return a transitional value (junk)
from a half-deleted kvp. At most, 64-bits worth of the kvp will be
written atomically, so using memset(...) to smear 0xFF's across a kvp
to free it left a lot to be desired.

Performance impact: very mild positive, thanks to FC for doing a
multi-thread host stack perf/scale test.

Added an ASSERT to catch attempts to add a (key,value) pair which
contains the magic "free kvp" value.

Type: fix

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I6a1aa8a2c30bc70bec4b696ce7b17c2839927065
This commit is contained in:
Dave Barach
2023-03-16 13:03:47 -04:00
committed by Florin Coras
parent 04bd0ea8e2
commit b9c8c57e98
18 changed files with 205 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
src/plugins/cnat/cnat_bihash.h
View File

@@ -44,11 +44,16 @@ typedef struct
u64 value[7];
} clib_bihash_kv_40_56_t;
static inline void
clib_bihash_mark_free_40_56 (clib_bihash_kv_40_56_t *v)
{
v->value[0] = 0xFEEDFACE8BADF00DULL;
}
static inline int
clib_bihash_is_free_40_56 (const clib_bihash_kv_40_56_t *v)
{
/* Free values are clib_memset to 0xff, check a bit... */
if (v->key[0] == ~0ULL && v->value[0] == ~0ULL)
if (v->value[0] == 0xFEEDFACE8BADF00DULL)
return 1;
return 0;
}

2
src/plugins/cnat/cnat_session.c
View File

@@ -238,7 +238,7 @@ cnat_session_scan (vlib_main_t * vm, f64 start_time, int i)
{
for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
{
if (v->kvp[k].key[0] == ~0ULL && v->kvp[k].value[0] == ~0ULL)
if (BV (clib_bihash_is_free) (&v->kvp[k]))
continue;
cnat_session_t *session = (cnat_session_t *) & v->kvp[k];