From: Eric Dumazet <[EMAIL PROTECTED]>
Date: Wed, 30 Jan 2008 09:08:56 +0100
> Current ip route cache implementation is not suited to large caches.
>
> We can consume a lot of CPU when cache must be invalidated, since we
> currently need to evict all cache entries, and this eviction is
> sometimes asynchronous. min_delay & max_delay can somewhat control this
> asynchronism behavior, but whole thing is a kludge, regularly triggering
> infamous soft lockup messages. When entries are still in use, this also
> consumes a lot of ram, filling dst_garbage.list.
>
> A better scheme is to use a generation identifier on each entry,
> so that cache invalidation can be performed by changing the table
> identifier, without having to scan all entries.
> No more delayed flushing, no more stalling when secret_interval expires.
>
> Invalidated entries will then be freed at GC time (controled by
> ip_rt_gc_timeout or stress), or when an invalidated entry is found
> in a chain when an insert is done.
> Thus we keep a normal equilibrium.
>
> This patch :
> - renames rt_hash_rnd to rt_genid (and makes it an atomic_t)
> - Adds a new rt_genid field to 'struct rtable' (filling a hole on 64bit)
> - Checks entry->rt_genid at appropriate places :
> --- Readers have to ignore invalidated entries.
> --- Writers can delete invalidated entries.
> - Removes rt_flush_timer timer
> - Removes unused /proc/sys/net/ipv4/{min_delay,max_delay}
>
> We even reduce size of route.o
>
> # size net/ipv4/route.o
> text data bss dec hex filename
> 20038 1331 160 21529 5419 net/ipv4/route.o.before
> 19991 1203 104 21298 5332 net/ipv4/route.o
>
> Next step will be to audit all rt_cache_flush(0) (aka flushes) users, see
> if they can be converted to "invalidate the cache" users.
>
> Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
This looks really nice, applied, thanks Eric.
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