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Nick Piggin a écrit : > On Friday 08 February 2008 13:13, Christoph Lameter wrote: >> are available in the git repository at: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/christoph/vm.git slub-linus >> >> (includes the cmpxchg_local fastpath since the cmpxchg_local work >> by Matheiu is in now, and the non atomic unlock by Nick. Verified that >> this is not doing any harm after some other patches had been removed. > > Ah, good. I think it is always a good thing to be able to remove atomics. > They place quite a bit of burden on the CPU, especially x86 where it also > has implicit memory ordering semantics (although x86 can speculatively > get around much of the problem, it's obviously worse than no restriction) > > Even if perhaps some cache coherency or timing quirk makes the non-atomic > version slower (all else being equal), then I'd still say that the non > atomic version should be preferred. > What about IRQ masking then ? Many CPU pay high cost for cli/sti pair... And SLAB/SLUB allocators, even if only used from process context, want to disable/re-enable interrupts... I understand kmalloc() want generic pools, but dedicated pools could avoid this cli/sti -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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