David S. Miller a écrit :
On Fri, 01 Apr 2005 23:05:37 +0200
Eric Dumazet <dada1@xxxxxxxxxxxxx> wrote:
You mean you prefer :
static spinlock_t *rt_hash_lock ; /* rt_hash_lock =
alloc_memory_at_boot_time(...) */
instead of
static spinlock_t rt_hash_lock[RT_HASH_LOCK_SZ] ;
In both cases, memory is taken from lowmem, and size of kernel image
is roughly the same (bss section takes no space in image)
In the former case the kernel image the bootloader has to
load is smaller. That's important, believe it or not. It
means less TLB entries need to be locked permanently into
the MMU on certain platforms.
OK thanks for this clarification. I changed to :
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
/*
* Instead of using one spinlock for each rt_hash_bucket, we use a table of
spinlocks
* The size of this table is a power of two and depends on the number of CPUS.
*/
#if NR_CPUS >= 32
#define RT_HASH_LOCK_SZ 4096
#elif NR_CPUS >= 16
#define RT_HASH_LOCK_SZ 2048
#elif NR_CPUS >= 8
#define RT_HASH_LOCK_SZ 1024
#elif NR_CPUS >= 4
#define RT_HASH_LOCK_SZ 512
#else
#define RT_HASH_LOCK_SZ 256
#endif
static spinlock_t *rt_hash_locks;
# define rt_hash_lock_addr(slot) &rt_hash_locks[slot & (RT_HASH_LOCK_SZ - 1)]
# define rt_hash_lock_init() { \
int i; \
rt_hash_locks = kmalloc(sizeof(spinlock_t) * RT_HASH_LOCK_SZ,
GFP_KERNEL); \
if (!rt_hash_locks) panic("IP: failed to allocate
rt_hash_locks\n"); \
for (i = 0; i < RT_HASH_LOCK_SZ; i++) \
spin_lock_init(&rt_hash_locks[i]); \
}
#else
# define rt_hash_lock_addr(slot) NULL
# define rt_hash_lock_init()
#endif
Are you OK if I also use alloc_large_system_hash() to allocate
rt_hash_table, instead of the current method ?
This new method is used in net/ipv4/tcp.c for tcp_ehash and tcp_bhash and
permits NUMA tuning.
Eric
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