[Crash-utility] [PATCH 1/2] symbols: optimize symname_hash with larger table and FNV-1a hash

Optimize the symbol name hash table to reduce collision and improve performance, especially on RISC-V architecture where symbol lookup is a hotspot. Changes: - Increase SYMNAME_HASH from 512 to 16384 (32x) to reduce collisions - Replace simple hash with FNV-1a algorithm for better distribution - Remove strlen() call, compute hash in single pass This reduces the average chain length in hash buckets significantly, improving symbol lookup performance at the cost of ~248KB additional memory. Signed-off-by: Rui Qi <qirui.001(a)bytedance.com&gt; --- defs.h | 2 +- symbols.c | 15 +++++++++------ 2 files changed, 10 insertions(+), 7 deletions(-) diff --git a/defs.h b/defs.h index a6f43725b6b8..4cf062894ebe 100644 --- a/defs.h +++ b/defs.h @@ -2900,7 +2900,7 @@ struct downsized { #define SYMVAL_HASH_INDEX(vaddr) \ (((vaddr) >> machdep->pageshift) % SYMVAL_HASH) -#define SYMNAME_HASH (512) +#define SYMNAME_HASH (16384) #define PATCH_KERNEL_SYMBOLS_START ((char *)(1)) #define PATCH_KERNEL_SYMBOLS_STOP ((char *)(2)) diff --git a/symbols.c b/symbols.c index e6865cabef74..afdf4a61cea2 100644 --- a/symbols.c +++ b/symbols.c @@ -1170,16 +1170,19 @@ symname_hash_init(void) static unsigned int symname_hash_index(char *name) { - unsigned int len, value; - unsigned char *array = (unsigned char *)name; + unsigned int hash = 2166136261U; + unsigned char *p = (unsigned char *)name; - len = strlen(name); - if (!len) + if (!*p) error(FATAL, "The length of the symbol name is zero!\n"); - value = array[len - 1] * array[len / 2]; + /* FNV-1a hash algorithm for better distribution */ + while (*p) { + hash ^= *p++; + hash *= 16777619; + } - return (array[0] ^ value) % SYMNAME_HASH; + return hash % SYMNAME_HASH; } /* -- 2.20.1