Messages in this thread | | | Date | Mon, 12 Dec 2005 09:57:31 -0200 | From | Marcelo Tosatti <> | Subject | Re: [RFC 3/6] Make nr_pagecache a per zone counter |
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On Mon, Dec 12, 2005 at 02:51:13PM +1100, Nick Piggin wrote: > Marcelo Tosatti wrote: > >On Sun, Dec 11, 2005 at 08:48:40PM +0100, Andi Kleen wrote: > > > >>>By the way, why does nr_pagecache needs to be an atomic variable on UP > >>>systems? > >> > >>At least on X86 UP atomic doesn't use the LOCK prefix and is thus quite > >>cheap. I would expect other architectures who care about UP performance > >>(= not IA64) to be similar. > > > > > >But in practice the variable does not need to be an atomic type for UP, but > >simply a word, since stores are atomic on UP systems, no? > > > >Several arches seem to use additional atomicity instructions on > >atomic functions: > > > > Yeah, this is to protect from interrupts and is common to most > load store architectures. It is possible we could have > atomic_xxx_irq / atomic_xxx_irqsave functions for these, however > I think nobody has yet demostrated the improvements outweigh the > complexity that would be added.
Hi Nick,
But nr_pagecache is not accessed at interrupt code, is it? It does not need to be an atomic type.
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