David S. Miller a écrit :
From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Date: Thu, 28 Jul 2005 17:52:04 +0200
[NET] : Adds prefetches in route hash list traversals.
The actual code doesnt use a prefetch enabled macro like
list_for_each_rcu(), so manually add prefetch() hints.
and the measured performance improvement is?
Half the improvement we could get if only fl.fl4_dst, and other fields were not
so far away from the u.rt_next field. (0xE8 on x86_64)
For good performance, one should of course choose a big route cache hash size, and in this case, prefetchs are useless, and even cost an
extra load : prefetch(rth->u.rt_next) imply the load of the rt_next pointer at the start of rth structure, while the fl fields are on a
different cache line)
But in case of DDOS, prefetches are a win.
I did not test a solution using two prefetches...
Other patches using prefetches will follow.