Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction abstraction

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To: <benh@...>
Cc: Ingo Molnar <mingo@...>, LKML <linux-kernel@...>, <x86@...>, xen-devel <xen-devel@...>, Thomas Gleixner <tglx@...>, Hugh Dickins <hugh@...>, Zachary Amsden <zach@...>, kvm-devel <kvm-devel@...>, Virtualization Mailing List <virtualization@...>, Rusty Russell <rusty@...>, Peter Zijlstra <a.p.zijlstra@...>, Linus Torvalds <torvalds@...>
Date: Wednesday, June 18, 2008 - 7:59 pm

Benjamin Herrenschmidt wrote:

Good point, I'd overlooked that.  I guess that means using it in 
ptep_set_wrprotect().

At present the x86 ptep_set_wrprotect() just uses clear_bit on the pte, 
which is a locked cycle.  Is that significantly cheaper than an xchg + 
set?  (Same number of locked operations...)

    J
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Messages in current thread:
[PATCH 0 of 4] mm+paravirt+xen: add pte read-modify-write ab..., Jeremy Fitzhardinge, (Mon Jun 16, 7:29 am)
[PATCH 2 of 4] paravirt: add hooks for ptep_modify_prot_star..., Jeremy Fitzhardinge, (Mon Jun 16, 7:30 am)
[PATCH 4 of 4] xen: add mechanism to extend existing multica..., Jeremy Fitzhardinge, (Mon Jun 16, 7:30 am)
[PATCH 3 of 4] xen: implement ptep_modify_prot_start/commit, Jeremy Fitzhardinge, (Mon Jun 16, 7:30 am)
[PATCH 1 of 4] mm: add a ptep_modify_prot transaction abstra..., Jeremy Fitzhardinge, (Mon Jun 16, 7:30 am)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Benjamin Herrenschmidt, (Wed Jun 18, 7:23 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Wed Jun 18, 7:59 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Wed Jun 18, 8:15 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Benjamin Herrenschmidt, (Wed Jun 18, 8:39 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Thu Jun 19, 1:03 am)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Benjamin Herrenschmidt, (Thu Jun 19, 3:20 am)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Thu Jun 19, 1:57 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Wed Jun 18, 8:37 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Fri Jun 20, 3:06 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Fri Jun 20, 4:05 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Fri Jun 20, 4:16 pm)
Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction ab..., Jeremy Fitzhardinge, (Fri Jun 20, 4:22 pm)