Hi David

This is based on a previous patch I sent 3 months ago, reduced to only the essential part, since
the previous version got no success in netdev (some people said they were working on this stuff but still no progress)

reminder of the bugfix :

The rt_check_expire() has a serious problem on machines with large
route caches, and a standard HZ value of 1000.

With default values, ie ip_rt_gc_interval = 60*HZ = 60000 ;

the loop count :

     for (t = ip_rt_gc_interval << rt_hash_log; t >= 0;


overflows (t is a 31 bit value) as soon rt_hash_log is >= 16  (65536
slots in route cache hash table).

In this case, rt_check_expire() does nothing at all


Thank you

Eric Dumazet


[NET] Scalability fixes in net/ipv4/route.c, bugfix in rt_check_expire

  - Locking abstraction
  - Spinlocks moved out of rt hash table : Less memory (50%) used by rt hash table. it's a win even on UP.
  - Sizing of spinlocks table depends on NR_CPUS
  - rt hash table allocated using alloc_large_system_hash() function
  - rt_check_expire() fixes (an overflow was possible)

Signed-off-by: Eric Dumazet <redacted>