Messages in this thread | | | Date | Fri, 30 May 2008 07:54:48 +0200 | From | Eric Dumazet <> | Subject | Re: [patch 02/41] cpu alloc: The allocator |
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Christoph Lameter a écrit : > On Fri, 30 May 2008, Eric Dumazet wrote: > > >>> +static DEFINE_PER_CPU(UNIT_TYPE, area[UNITS]); >>> >>> >> area[] is not guaranteed to be aligned on anything but 4 bytes. >> >> If someone then needs to call cpu_alloc(8, GFP_KERNEL, 8), it might get an non >> aligned result. >> >> Either you should add an __attribute__((__aligned__(PAGE_SIZE))), >> or take into account the real address of area[] in cpu_alloc() to avoid waste >> of up to PAGE_SIZE bytes >> per cpu. >> > > I think cacheline aligning should be sufficient. People should not > allocate large page aligned objects here. > > > Hum, maybe, but then we broke modules that might request up to PAGE_SIZE alignement for their percpu section, if I read your 3rd patch correctly.
Taking into account the ((unsigned long)area & (PAGE_SIZE-1)) offset in cpu_alloc() should give up to PAGE_SIZE alignment for free.
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