Messages in this thread | | | Date | Wed, 14 Dec 2005 19:29:04 -0800 | From | Matt Mackall <> | Subject | Re: [RFC][PATCH 1/6] Create Critical Page Pool |
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On Wed, Dec 14, 2005 at 08:26:09AM -0800, Matthew Dobson wrote: > Rik van Riel wrote: > > On Tue, 13 Dec 2005, Matthew Dobson wrote: > > > > > >>Create the basic Critical Page Pool. Any allocation specifying > >>__GFP_CRITICAL will, as a last resort before failing the allocation, try > >>to get a page from the critical pool. For now, only singleton (order 0) > >>pages are supported. > > > > > > How are you going to limit the number of GFP_CRITICAL > > allocations to something smaller than the number of > > pages in the pool ? > > We can't. > > > > Unless you can do that, all guarantees are off... > > Well, I was careful not to use the word guarantee in my post. ;) The idea > is not to offer a 100% guarantee that the pool will never be exhausted. > The idea is to offer a pool that, sized appropriately, offers a very good > chance of surviving your emergency situation. The definition of what is a > critical allocation and what the emergency situation is left intentionally > somewhat vague, so as to offer more flexibility. For our use, certain > networking allocations are critical and our emergency situation is a 2 > minute window of potential exreme memory pressure. For others it could be > something completely different, but the expectation is that the emergency > situation would be of a finite time, since the pool is a fixed size.
What's your plan for handling the no-room-to-receive-ACKs problem?
Without addressing this, this is a non-starter for most of the network OOM problems I care about.
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