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Date: Tue, 10 May 2011 09:20:38 +0900 (JST)
From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To: Stephen Wilson <wilsons@...rt.ca>
Cc: kosaki.motohiro@...fujitsu.com,
Andrew Morton <akpm@...ux-foundation.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Hugh Dickins <hughd@...gle.com>,
David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] mm: use walk_page_range() instead of custom page table walking code
> On Mon, May 09, 2011 at 04:38:49PM +0900, KOSAKI Motohiro wrote:
> > Hello,
> >
> > sorry for the long delay.
>
> Please, no apologies. Thank you for the review!
>
> > > In the specific case of show_numa_map(), the custom page table walking
> > > logic implemented in mempolicy.c does not provide any special service
> > > beyond that provided by walk_page_range().
> > >
> > > Also, converting show_numa_map() to use the generic routine decouples
> > > the function from mempolicy.c, allowing it to be moved out of the mm
> > > subsystem and into fs/proc.
> > >
> > > Signed-off-by: Stephen Wilson <wilsons@...rt.ca>
> > > ---
> > > mm/mempolicy.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++-------
> > > 1 files changed, 46 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > > index 5bfb03e..dfe27e3 100644
> > > --- a/mm/mempolicy.c
> > > +++ b/mm/mempolicy.c
> > > @@ -2568,6 +2568,22 @@ static void gather_stats(struct page *page, void *private, int pte_dirty)
> > > md->node[page_to_nid(page)]++;
> > > }
> > >
> > > +static int gather_pte_stats(pte_t *pte, unsigned long addr,
> > > + unsigned long pte_size, struct mm_walk *walk)
> > > +{
> > > + struct page *page;
> > > +
> > > + if (pte_none(*pte))
> > > + return 0;
> > > +
> > > + page = pte_page(*pte);
> > > + if (!page)
> > > + return 0;
> >
> > original check_pte_range() has following logic.
> >
> > orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> > do {
> > struct page *page;
> > int nid;
> >
> > if (!pte_present(*pte))
> > continue;
> > page = vm_normal_page(vma, addr, *pte);
> > if (!page)
> > continue;
> > /*
> > * vm_normal_page() filters out zero pages, but there might
> > * still be PageReserved pages to skip, perhaps in a VDSO.
> > * And we cannot move PageKsm pages sensibly or safely yet.
> > */
> > if (PageReserved(page) || PageKsm(page))
> > continue;
> > gather_stats(page, private, pte_dirty(*pte));
> >
> > Why did you drop a lot of check? Is it safe?
>
> I must have been confused. For one, walk_page_range() does not even
> lock the pmd entry when iterating over the pte's. I completely
> overlooked that fact and so with that, the series is totally broken.
>
> I am currently testing a slightly reworked set based on the following
> variation. When finished I will send v2 of the series which will
> address all issues raised so far.
>
> Thanks again for the review!
>
>
>
> From 013a1e0fc96f8370339209f16d81df4ded40dbf2 Mon Sep 17 00:00:00 2001
> From: Stephen Wilson <wilsons@...rt.ca>
> Date: Mon, 9 May 2011 14:39:27 -0400
> Subject: [PATCH] mm: use walk_page_range() instead of custom page table
> walking code
>
> Converting show_numa_map() to use the generic routine decouples
> the function from mempolicy.c, allowing it to be moved out of the mm
> subsystem and into fs/proc.
>
> Also, include KSM pages in /proc/pid/numa_maps statistics. The pagewalk
> logic implemented by check_pte_range() failed to account for such pages
> as they were not applicable to the page migration case.
Seems very reasonable change.
>
> Signed-off-by: Stephen Wilson <wilsons@...rt.ca>
> ---
> mm/mempolicy.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
> 1 files changed, 68 insertions(+), 7 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 5bfb03e..945e85d 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2531,6 +2531,7 @@ int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol, int no_context)
> }
>
> struct numa_maps {
> + struct vm_area_struct *vma;
> unsigned long pages;
> unsigned long anon;
> unsigned long active;
> @@ -2568,6 +2569,41 @@ static void gather_stats(struct page *page, void *private, int pte_dirty)
> md->node[page_to_nid(page)]++;
> }
>
> +static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
> + unsigned long end, struct mm_walk *walk)
> +{
> + struct numa_maps *md;
> + spinlock_t *ptl;
> + pte_t *orig_pte;
> + pte_t *pte;
> +
> + md = walk->private;
> + orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
> + do {
> + struct page *page;
> + int nid;
> +
> + if (!pte_present(*pte))
> + continue;
> +
> + page = vm_normal_page(md->vma, addr, *pte);
> + if (!page)
> + continue;
> +
> + if (PageReserved(page))
> + continue;
> +
> + nid = page_to_nid(page);
> + if (!node_isset(nid, node_states[N_HIGH_MEMORY]))
> + continue;
> +
> + gather_stats(page, md, pte_dirty(*pte));
> +
> + } while (pte++, addr += PAGE_SIZE, addr != end);
> + pte_unmap_unlock(orig_pte, ptl);
> + return 0;
> +}
Looks completely good.
Reviewed-by KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Thank you for great work!
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