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Message-ID: <CAKgT0UdydVv7yy-2AQ93aAKkNngC5dWwOnBS4GoDv6T84p4K4Q@mail.gmail.com> Date: Fri, 27 Jul 2012 12:06:47 -0700 From: Alexander Duyck <alexander.duyck@...il.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, David Miller <davem@...emloft.net>, netdev@...r.kernel.org Subject: Re: [PATCH 00/16] Remove the ipv4 routing cache On Fri, Jul 27, 2012 at 9:28 AM, Eric Dumazet <eric.dumazet@...il.com> wrote: > On Fri, 2012-07-27 at 09:23 -0700, Eric W. Biederman wrote: > >> I am familiar. But does hardware prefetching make a difference >> if your object is less than 64 bytes? >> > > Apparently yes, if the prefetch touches a dirtied neighbour cache line. > >> I don't believe only allocating 64 bytes will be a problem, >> as no one else well be dirtying your cache line. >> >> I suppose you could run into pathologies where your object >> is 3*64 bytes in size, but your expression doesn't handle >> that case either. >> > > Sure, but in most cases fib objects are under 128 bytes. > > >> The other alternative to guarantee very good cache behavior is >> to ensure you are allocating a power of two size up to some limit, >> perhaps page size. >> > > Good idea. > >> My point is the magic 128 likely requires an explicatory comment and I >> think the net result is you have encoded something fragile that is good >> for testing but that will in the fullness of time do strange things that >> will be easy to overlook. > > Sure, I'll send a v2, thanks. > > I tested out v1 of your patch and didn't seem much of a change in my test environment. I figure I will spend most of today going through the code trying to figure out what is causing the issues I am seeing and why your changes had no effect on my setup. Thanks, Alex -- 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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