Re: [PATCH 0/9] Add apply_to_page_range_batch() and use it
From: Andrew Morton
Date: Thu Jan 27 2011 - 19:18:58 EST
On Mon, 24 Jan 2011 14:55:58 -0800
Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> I'm proposing this series for 2.6.39.
> We've had apply_to_page_range() for a while, which is a general way to
> apply a function to ptes across a range of addresses - including
> allocating any missing parts of the pagetable as needed. This logic
> is replicated in a number of places throughout the kernel, but it
> hasn't been widely replaced by this function, partly because of
> concerns about the overhead of calling the function once per pte.
> This series adds apply_to_page_range_batch() (and reimplements
> apply_to_page_range() in terms of it), which calls the pte operation
> function once per pte page, moving the inner loop into the callback
> apply_to_page_range(_batch) also calls its callback with lazy mmu
> updates enabled, which allows batching of the operations in
> environments where this is beneficial (ie, virtualization). The only
> caveat this introduces is callbacks can't expect to immediately see
> the effects of the pte updates in memory.
> Since this is effectively identical to the code in lib/ioremap.c and
> mm/vmalloc.c (twice!), I replace their open-coded variants. I'm sure
> there are others places in the kernel which could do with this (I only
> stumbled over ioremap by accident).
> I also add a minor optimisation to vunmap_page_range() to use a
> plain pte_clear() rather than the more expensive and unnecessary
> Jeremy Fitzhardinge (9):
> mm: remove unused "token" argument from apply_to_page_range callback.
> mm: add apply_to_page_range_batch()
> ioremap: use apply_to_page_range_batch() for ioremap_page_range()
> vmalloc: use plain pte_clear() for unmaps
> vmalloc: use apply_to_page_range_batch() for vunmap_page_range()
> vmalloc: use apply_to_page_range_batch() for
> vmalloc: use apply_to_page_range_batch() in alloc_vm_area()
> xen/mmu: use apply_to_page_range_batch() in
> xen/grant-table: use apply_to_page_range_batch()
> arch/x86/xen/grant-table.c | 30 +++++----
> arch/x86/xen/mmu.c | 18 +++--
> include/linux/mm.h | 9 ++-
> lib/ioremap.c | 85 +++++++------------------
> mm/memory.c | 57 ++++++++++++-----
> mm/vmalloc.c | 150 ++++++++++++--------------------------------
> 6 files changed, 140 insertions(+), 209 deletions(-)
That all looks good to me.
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