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Date: Fri, 27 Jul 2012 17:12:29 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: "Eric W. Biederman" <ebiederm@...ssion.com> Cc: David Miller <davem@...emloft.net>, alexander.duyck@...il.com, netdev@...r.kernel.org Subject: Re: [PATCH 00/16] Remove the ipv4 routing cache On Fri, 2012-07-27 at 07:53 -0700, Eric W. Biederman wrote: > Eric Dumazet <eric.dumazet@...il.com> writes: > > > Now IP route cache is removed, we should make sure fib structures > > cant share cache lines with possibly often dirtied objects. > > > > On x86, kmalloc-96 cache can be source of such problems. > > > > Signed-off-by: Eric Dumazet <edumazet@...gle.com> > > > > +static inline void *fib_zalloc(size_t size) > > +{ > > + /* We want to avoid possible false sharing */ > > + return kzalloc(max_t(size_t, 128, size), GFP_KERNEL); > > Why the hard coded 128 here? > > It seems more portable and obvious to do > return kzalloc(round_up(size, L1_CACHE_BYTES), GFP_KERNEL); > Its not that obvious, because some machines have an apparent L1_CACHE_BYTES of 64, but hardware prefetching to 128 bytes But using 2*L1_CACHE_BYTES as minimum allocation size might be overkill on some arches with 256 bytes cache lines. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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