From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <462D6866.8030207@yahoo.com.au> Date: Tue, 24 Apr 2007 12:16:06 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [PATCH] lazy freeing of memory through MADV_FREE References: <46247427.6000902@redhat.com> <20070420135715.f6e8e091.akpm@linux-foundation.org> <462932BE.4020005@redhat.com> <20070420150618.179d31a4.akpm@linux-foundation.org> <4629524C.5040302@redhat.com> <462ACA40.8070407@yahoo.com.au> <462B0156.9020407@redhat.com> <462BFAF3.4040509@yahoo.com.au> <462C2DC7.5070709@redhat.com> <462C2F33.8090508@redhat.com> <462C7A6F.9030905@redhat.com> <462C88B1.8080906@yahoo.com.au> <462C8B0A.8060801@redhat.com> <462C8BFF.2050405@yahoo.com.au> <462C8E1D.8000706@redhat.com> <462D5A2E.5060908@yahoo.com.au> <462D643C.5020709@redhat.com> In-Reply-To: <462D643C.5020709@redhat.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: Andrew Morton , linux-kernel , linux-mm , shak , jakub@redhat.com, drepper@redhat.com List-ID: Rik van Riel wrote: > This should fix the MADV_FREE code for PPC's hashed tlb. > > Signed-off-by: Rik van Riel > --- > > Nick Piggin wrote: > >>> Nick Piggin wrote: >>> >>>>> 3) because of this, we can treat any such accesses as >>>>> happening simultaneously with the MADV_FREE and >>>>> as illegal, aka undefined behaviour territory and >>>>> we do not need to worry about them >>>> >>>> >>>> >>>> Yes, but I'm wondering if it is legal in all architectures. >>> >>> >>> >>> It's similar to trying to access memory during an munmap. >>> >>> You may be able to for a short time, but it'll come back to >>> haunt you. >> >> >> The question is whether the architecture specific tlb >> flushing code will break or not. > > > I guess we'll need to call tlb_remove_tlb_entry() inside the > MADV_FREE code to keep powerpc happy. > > Thanks for pointing this one out. > >>> Even then we do. Each invocation of zap_pte_range() only touches >>> one page table page, and it flushes the TLB before releasing the >>> page table lock. >> >> >> What kernel are you looking at? -rc7 and rc6-mm1 don't, AFAIKS. > > > Oh dear. I see it now... > > The tlb end things inside zap_pte_range() are actually > noops and the actual tlb flush only happens inside > zap_page_range(). > > I guess the fact that munmap gets the mmap_sem for > writing should save us, though... What about an unmap_mapping_range, or another MADV_FREE or MADV_DONTNEED? > > > ------------------------------------------------------------------------ > > --- linux-2.6.20.x86_64/mm/memory.c.noppc 2007-04-23 21:50:09.000000000 -0400 > +++ linux-2.6.20.x86_64/mm/memory.c 2007-04-23 21:48:59.000000000 -0400 > @@ -679,6 +679,7 @@ static unsigned long zap_pte_range(struc > } > ptep_test_and_clear_dirty(vma, addr, pte); > ptep_test_and_clear_young(vma, addr, pte); > + tlb_remove_tlb_entry(tlb, pte, addr); > SetPageLazyFree(page); > if (PageActive(page)) > deactivate_tail_page(page); -- SUSE Labs, Novell Inc. -- 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-mm.org/ . Don't email: email@kvack.org