From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 26 May 2000 10:35:30 -0700 (PDT) From: Matthew Dillon Message-Id: <200005261735.KAA90570@apollo.backplane.com> Subject: Re: [RFC] 2.3/4 VM queues idea References: <200005251618.JAA82894@apollo.backplane.com> <20000525185059.A20563@pcep-jamie.cern.ch> <20000526120805.C10082@redhat.com> <20000526132219.C21510@pcep-jamie.cern.ch> <20000526141526.E10082@redhat.com> <20000526163129.B21662@pcep-jamie.cern.ch> <20000526153821.N10082@redhat.com> <20000526183640.A21731@pcep-jamie.cern.ch> <20000526174018.Q10082@redhat.com> <200005261655.JAA90389@apollo.backplane.com> <20000526190555.B21856@pcep-jamie.cern.ch> Sender: owner-linux-mm@kvack.org Return-Path: To: Jamie Lokier Cc: "Stephen C. Tweedie" , Rik van Riel , linux-mm@kvack.org List-ID: :Matthew Dillon wrote: :> In regards to overhead, anything that collects a bunch of pages together :> (e.g. vm_map_entry, vm_object under FBsd, VMA in Jamie's scheme) :> simply does not create a memory overhead issue. None at all. It's :> the things that eat memory on a per-page basis that get annoying. : :Stephen's point is that there are applications which use mprotect() on a :per-page basis. Some garbage collectors for example, to track dirtied :pages. : :And having to scan hundreds of vmas to find one pte sucks :-) : :But I addressed that a few minutes ago. In my scheme you don't have to :scan lots of vmas to find that pte. Only one or two, or you can choose :to increase that number while decreasing memory requirements a little. : :-- Jamie Hmm. I know apps which use madvise() to manage allocated/free pages efficiently, but not any that use mprotect(). The madvise() flags typically used effect the underlying pages directly and should not fragment the VMA's at all. In anycase, it's not a big deal because even if you did have to fragment the VMA's, you can still collapse adjacent entries together. i.e. if the garbage collector protects page 1 and then later on protects page 2 the same way, you still need only one VMA to represent both pages. -Matt Matthew Dillon -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux.eu.org/Linux-MM/