Messages in this thread |  | | | Date | Sat, 23 Feb 2002 12:27:33 -0800 | | From | Andrew Morton <> | | Subject | Re: [PATCH] only irq-safe atomic ops |
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Stephen Lord wrote: > > Andrew Morton wrote: > > >Robert Love wrote: > > > >>... > >> > >>Question: if (from below) you are going to use atomic operations, why > >>make it per-CPU at all? Just have one counter and atomic_inc and > >>atomic_read it. You won't need a spin lock. > >> > > > >Oh that works fine. But then it's a global counter, so each time > >a CPU marks a page dirty, the counter needs to be pulled out of > >another CPU's cache. Which is not a thing I *need* to do. > > > >As I said, it's a micro-issue. But it's a requirement which > >may pop up elsewhere. > > > > > I can tell you that Irix has just such a global counter for the amount of > delayed allocate pages - and it gets to be a major point of cache contention > once you get to larger cpu counts. So avoiding that from the start would > be good.
Ah, good info. Thanks. I'll fix it with a big "FIXME" comment for now, fix it for real when Rusty's per-CPU infrastructure appears.
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