RE: [Lhms-devel] Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

RE: [Lhms-devel] Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Tolentino, Matthew E]

>> Followings are patches for removing bitmaps from buddy 
>allocator, against 2.6.9-rc3.
>> I think this version is much clearer than ones I posted a month ago.
>...
>> If there is unclear point, please tell me.
>
>What was the purpose behind this, again? Sorry, has been too long since
>I last looked.
>

For one, it avoids the otherwise requisite resizing of the bitmaps 
during memory hotplug operations...

matt
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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Dave Hansen]

On Thu, 2004-10-07 at 08:03, Tolentino, Matthew E wrote:
> >> Followings are patches for removing bitmaps from buddy=20
> >allocator, against 2.6.9-rc3.
> >> I think this version is much clearer than ones I posted a month ago.
> >...
> >> If there is unclear point, please tell me.
> >
> >What was the purpose behind this, again? Sorry, has been too long since
> >I last looked.
> 
> For one, it avoids the otherwise requisite resizing of the bitmaps=20
> during memory hotplug operations...

It also simplifies the nonlinear implementation.  The whole reason we
had the lpfn (Linear) stuff was so that the bitmaps could represent a
sparse physical address space in a much more linear fashion.  With no
bitmaps, this isn't an issue, and gets rid of a lot of code, and a
*huge* source of bugs where lpfns and pfns are confused for each other. 
-- Dave

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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Martin J. Bligh]

--Dave Hansen <haveblue@us.ibm.com> wrote (on Thursday, October 07, 2004 08:39:38 -0700):

> On Thu, 2004-10-07 at 08:03, Tolentino, Matthew E wrote:
>> >> Followings are patches for removing bitmaps from buddy=20
>> > allocator, against 2.6.9-rc3.
>> >> I think this version is much clearer than ones I posted a month ago.
>> > ...
>> >> If there is unclear point, please tell me.
>> > 
>> > What was the purpose behind this, again? Sorry, has been too long since
>> > I last looked.
>> 
>> For one, it avoids the otherwise requisite resizing of the bitmaps=20
>> during memory hotplug operations...
> 
> It also simplifies the nonlinear implementation.  The whole reason we
> had the lpfn (Linear) stuff was so that the bitmaps could represent a
> sparse physical address space in a much more linear fashion.  With no
> bitmaps, this isn't an issue, and gets rid of a lot of code, and a
> *huge* source of bugs where lpfns and pfns are confused for each other. 

Makese sense on both counts. Would be nice to add the justification to 
the changelog ;-)

M.

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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Dave Hansen]

On Thu, 2004-10-07 at 08:57, Martin J. Bligh wrote:
> Makese sense on both counts. Would be nice to add the justification to 
> the changelog ;-)

Would you mind running these through your normal set of tests on the
NUMAQ?  The last time I ran them, I didn't see a performance impact
either way, and I'd be good to check again.

-- Dave

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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Martin J. Bligh]

--Dave Hansen <haveblue@us.ibm.com> wrote (on Thursday, October 07, 2004 09:10:19 -0700):

> On Thu, 2004-10-07 at 08:57, Martin J. Bligh wrote:
>> Makese sense on both counts. Would be nice to add the justification to 
>> the changelog ;-)
> 
> Would you mind running these through your normal set of tests on the
> NUMAQ?  The last time I ran them, I didn't see a performance impact
> either way, and I'd be good to check again.

Will do. What they're doing looks like it might be expensive. will check.

M.

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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Martin J. Bligh]

>> Makese sense on both counts. Would be nice to add the justification to 
>> the changelog ;-)
> 
> Would you mind running these through your normal set of tests on the
> NUMAQ?  The last time I ran them, I didn't see a performance impact
> either way, and I'd be good to check again.

Makes no difference in performance that I can see.

M.

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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Hiroyuki KAMEZAWA]

Martin J. Bligh wrote:
 >>>>What was the purpose behind this, again? Sorry, has been too long since
 >>>>I last looked.

>>On Thu, 2004-10-07 at 08:03, Tolentino, Matthew E wrote:
>>
>>For one, it avoids the otherwise requisite resizing of the bitmaps=20
>>during memory hotplug operations...
>>

 >> Dave McCracken wrote:
>> The memory allocator bitmaps are the main remaining reason we need the
>> concept of linear memory.  If we can get rid of them, it's one step closer
>> to managing memory as a set of sections.

 >>--Dave Hansen <haveblue@us.ibm.com> wrote (on Thursday, October 07, 2004 08:39:38 -0700)
>>It also simplifies the nonlinear implementation.  The whole reason we
>>had the lpfn (Linear) stuff was so that the bitmaps could represent a
>>sparse physical address space in a much more linear fashion.  With no
>>bitmaps, this isn't an issue, and gets rid of a lot of code, and a
>>*huge* source of bugs where lpfns and pfns are confused for each other. 
> 
> 
> Makese sense on both counts. Would be nice to add the justification to 
> the changelog ;-)
> 

It seems all I should answer is already answered.
Thank you all.

I'll add the purpose to the changelog.

Kame <kamezawa.hiroyu@jp.fujitsu.com>

> M.
> 

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[PATCH] no buddy bitmap patch : intro and includes [0/2]

[Hiroyuki KAMEZAWA]

Hi,

Followings are patches for removing bitmaps from buddy allocator, against 2.6.9-rc3.
I think this version is much clearer than ones I posted a month ago.

The problem I was worried about was how to deal with memmap's holes in a zone.
and I decided to use pfn_valid() simply. Now, there is no messy codes :)

pfn_valid() is used when macro "HOLES_IN_ZONE" is defined.
It is defined only in ia64 now.

Here is kernbench result on my tiger4 (Itanium2 1.3GHz x2, 8 Gbytes memory)

Average Optimal -j 8 Load Run (Perfroming 5 run of make -j 8 on linux-2.6.8 source tree):

                Elapsed Time  User Time  System Time Percent CPU  Context Switches   Sleeps
2.6.9-rc3         699.906      1322.01     39.336       194            64390         74416.8
no-bitmap         698.334      1321.79     38.58        194.2          64435.4       74622.2

If there is unclear point, please tell me.

Thanks.
Kame <kamezawa.hiroyu@jp.fujitsu.com>

=== patch for include files ===

This patch removes bitmap from zone->free_area[] in include/linux/mmzone.h,
and adds some comments on page->private field in include/linux/mm.h.

non-atomic ops for changing PG_private bit is added in include/page-flags.h.
zone->lock is always acquired when PG_private of "a free page" is changed.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


---

 test-kernel-kamezawa/include/linux/mm.h         |    2 ++
 test-kernel-kamezawa/include/linux/mmzone.h     |    1 -
 test-kernel-kamezawa/include/linux/page-flags.h |    2 ++
 3 files changed, 4 insertions(+), 1 deletion(-)

diff -puN include/linux/mm.h~eliminate-bitmap-includes include/linux/mm.h
--- test-kernel/include/linux/mm.h~eliminate-bitmap-includes	2004-10-07 17:18:34.062982800 +0900
+++ test-kernel-kamezawa/include/linux/mm.h	2004-10-07 17:18:34.070981584 +0900
@@ -209,6 +209,8 @@ struct page {
 					 * usually used for buffer_heads
 					 * if PagePrivate set; used for
 					 * swp_entry_t if PageSwapCache
+					 * When page is free, this indicates
+					 * order in the buddy system.
 					 */
 	struct address_space *mapping;	/* If low bit clear, points to
 					 * inode address_space, or NULL.
diff -puN include/linux/mmzone.h~eliminate-bitmap-includes include/linux/mmzone.h
--- test-kernel/include/linux/mmzone.h~eliminate-bitmap-includes	2004-10-07 17:18:34.065982344 +0900
+++ test-kernel-kamezawa/include/linux/mmzone.h	2004-10-07 17:18:34.071981432 +0900
@@ -22,7 +22,6 @@

 struct free_area {
 	struct list_head	free_list;
-	unsigned long		*map;
 };

 struct pglist_data;
diff -puN include/linux/page-flags.h~eliminate-bitmap-includes include/linux/page-flags.h
--- test-kernel/include/linux/page-flags.h~eliminate-bitmap-includes	2004-10-07 17:18:34.067982040 +0900
+++ test-kernel-kamezawa/include/linux/page-flags.h	2004-10-07 17:18:34.071981432 +0900
@@ -238,6 +238,8 @@ extern unsigned long __read_page_state(u
 #define SetPagePrivate(page)	set_bit(PG_private, &(page)->flags)
 #define ClearPagePrivate(page)	clear_bit(PG_private, &(page)->flags)
 #define PagePrivate(page)	test_bit(PG_private, &(page)->flags)
+#define __SetPagePrivate(page)  __set_bit(PG_private, &(page)->flags)
+#define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)

 #define PageWriteback(page)	test_bit(PG_writeback, &(page)->flags)
 #define SetPageWriteback(page)						\

_

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Re: [PATCH] no buddy bitmap patch : intro and includes [0/2]

[Martin J. Bligh]

> Followings are patches for removing bitmaps from buddy allocator, against 2.6.9-rc3.
> I think this version is much clearer than ones I posted a month ago.
...
> If there is unclear point, please tell me.

What was the purpose behind this, again? Sorry, has been too long since
I last looked.

M.

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