On 05/15/2015 01:43 PM, Kirill A. Shutemov wrote:
On Fri, May 15, 2015 at 01:33:31PM +0200, Vlastimil Babka wrote:
On 05/15/2015 12:56 PM, Kirill A. Shutemov wrote:
On Thu, May 14, 2015 at 04:12:29PM +0200, Vlastimil Babka wrote:
On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote:
With new refcounting all subpages of the compound page are not nessessary
have the same mapcount. We need to take into account mapcount of every
sub-page.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Tested-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
(some nitpicks below)
---
fs/proc/task_mmu.c | 43 ++++++++++++++++++++++---------------------
1 file changed, 22 insertions(+), 21 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 956b75d61809..95bc384ee3f7 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -449,9 +449,10 @@ struct mem_size_stats {
};
static void smaps_account(struct mem_size_stats *mss, struct page *page,
- unsigned long size, bool young, bool dirty)
+ bool compound, bool young, bool dirty)
{
- int mapcount;
+ int i, nr = compound ? hpage_nr_pages(page) : 1;
Why not just HPAGE_PMD_NR instead of hpage_nr_pages(page)?
Okay, makes sense. Compiler is smart enough to optimize away HPAGE_PMD_NR
for THP=n. (HPAGE_PMD_NR is BUILD_BUG() for THP=n)
Ah, BUILD_BUG()... I'm not sure we can rely on optimization to avoid
BUILD_BUG(), what if somebody compiles with all optimizations off?
Kernel relies on dead-code elimination. You cannot build kernel with -O0.
Ah, OK.
So why not replace BUILD_BUG() with "1", or create a variant of HPAGE_PMD_NR
that does that, for this case and patch 3. Seems better than testing
PageTransHuge everywhere...
I think we could try to downgrade it BUG(). Although I found BUILD_BUG()
useful few times.
BUILD_BUG() seems like a better match here. Better than pollute the code
for THP=n (in case of Patch 3 where it doesn't eliminate).
HPAGE_PMD_NR==1 would be just wrong. It would mean you can map order-0
page with PMD %-|
That's why I suggested a different variant of the "variable".
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