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Date: Sat, 5 Apr 2008 02:23:30 +0200 From: Andrea Arcangeli <andrea@...ranet.com> To: Christoph Lameter <clameter@....com> Cc: Hugh Dickins <hugh@...itas.com>, Robin Holt <holt@....com>, Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>, kvm-devel@...ts.sourceforge.net, Peter Zijlstra <a.p.zijlstra@...llo.nl>, general@...ts.openfabrics.org, Steve Wise <swise@...ngridcomputing.com>, Roland Dreier <rdreier@...co.com>, Kanoj Sarcar <kanojsarcar@...oo.com>, steiner@....com, linux-kernel@...r.kernel.org, linux-mm@...ck.org, daniel.blueman@...drics.com, Nick Piggin <npiggin@...e.de> Subject: Re: [PATCH] mmu notifier #v11 On Fri, Apr 04, 2008 at 03:06:18PM -0700, Christoph Lameter wrote: > Adds some comments. Still objectionable is the multiple ways of > invalidating pages in #v11. Callout now has similar locking to emm. range_begin exists because range_end is called after the page has already been freed. invalidate_page is called _before_ the page is freed but _after_ the pte has been zapped. In short when working with single pages it's a waste to block the secondary-mmu page fault, because it's zero cost to invalidate_page before put_page. Not even GRU need to do that. Instead for the multiple-pte-zapping we have to call range_end _after_ the page is already freed. This is so that there is a single range_end call for an huge amount of address space. So we need a range_begin for the subsystems not using page pinning for example. When working with single pages (try_to_unmap_one, do_wp_page) invalidate_page avoids to block the secondary mmu page fault, and it's in turn faster. Besides avoiding need of serializing the secondary mmu page fault, invalidate_page also reduces the overhead when the mmu notifiers are disarmed (i.e. kvm not running). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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