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Date: Tue, 7 Aug 2012 23:44:34 +0100 From: Ben Hutchings <bhutchings@...arflare.com> To: Eric Dumazet <eric.dumazet@...il.com> CC: David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH] net: force dst_default_metrics to const section On Wed, 2012-08-08 at 00:34 +0200, Eric Dumazet wrote: > On Tue, 2012-08-07 at 23:12 +0100, Ben Hutchings wrote: > > On Tue, 2012-08-07 at 22:55 +0200, Eric Dumazet wrote: > > > From: Eric Dumazet <edumazet@...gle.com> > > > > > > > > > > Some day the compiler may be smart enough to ignore the different > > > > between explicit and implicit zero-initialisation, and put it back in > > > > BSS. Declaring this __cache_aligned_in_smp might be a better option. > > > > > > __cache_aligned_in_smp aligns start of the structure, but can be > > > followed by another var in same cache line. Yes, this is bad. > > > > Oh, that's unexpected. > > > > > By the way we dont care of cache alignment on this structure, only it > > > should be const. Its a soft requirement, machine wont crash if it is not > > > the case. > > > > Right. > > > > > If compiler is smart one day as you say (it should first be non buggy > > > IMHO), then we can add a non zero field like this : > > [...] > > > > That would work, but it's ugly! How about defining and using a > > meaningfully-named macro that expands to __section(.rodata)? > > You are kidding. I prefer plain C and not having to mess with all > arches. Any consideration of implementation details like BSS and cache line sharing is already outside of 'plain C'. And you don't have to 'mess with all arches'; just look at what <linux/init.h> and <linux/module.h> do. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- 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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