zsmalloc: Add Kconfig for enabling PTE method
Subsystems (2)
PATCH 1/1 zsmalloc: Add Kconfig for enabling PTE method
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].
But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new Kconfig to select the approach.
This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)
drivers/staging/zsmalloc/Kconfig +12 -0
@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmalloc
drivers/staging/zsmalloc/zsmalloc-main.c +0 -11
@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1) -/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here -* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif -struct mapping_area {#ifdef USE_PGTABLE_MAPPING struct vm_struct *vm;/* vm area for mapping object that span pages */
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Quoted 9 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
What's the meaning of 'zs' in zsmalloc? It's short for what?
Quoted 46 lines
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +12
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmallocdrivers/staging/zsmalloc/zsmalloc-main.c +0
-4@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1) -/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here
drivers/staging/zsmalloc/zsmalloc-main.c struct zs_pool { · line 223
Quoted 10 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-7-* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif -struct mapping_area {#ifdef USE_PGTABLE_MAPPING struct vm_struct *vm;/* vm area for mapping object that span pages */
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Quoted 5 lines · Simon Jeons
Quoted 4 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].
Quoted 7 lines
Quoted 5 lines
But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
What's the meaning of 'zs' in zsmalloc? It's short for what?
I'm not right person to answer but I guess it stands for compressed slab.
Signature · 8 lines
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Greg Kroah-Hartman
maintainerQuoted 51 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +12
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmallocdrivers/staging/zsmalloc/zsmalloc-main.c +0
-0@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)
drivers/staging/zsmalloc/zsmalloc-main.c struct zs_pool { · line 230
Quoted 10 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-10-/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here -* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif
Did you test this? I don't see the new config value you added actually do anything in this code. Also, if I select it incorrectly on ARM, or or other platforms, what is keeping this from doing bad things?
thanks,
greg k-h
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Hi Greg,
Quoted 52 lines · Greg Kroah-Hartman
Quoted 51 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +12
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmallocdrivers/staging/zsmalloc/zsmalloc-main.c +0
-0@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)
Quoted 13 lines
drivers/staging/zsmalloc/zsmalloc-main.c struct zs_pool { · line 230
Quoted 10 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-10-/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here -* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif Did you test this? I don't see the new config value you added actually do anything in this code. Also, if I select it incorrectly on ARM, or
*slaps self*
Quoted 1 line
or other platforms, what is keeping this from doing bad things?
There is no way to prevent it now.
I thought a way to detect it dynamically by testing performance both approaches in booting/module-loading time and select the best choice. For it, we should add benchmark code and delay booting/module-loading, it's not good for embedded system because they are fighting with 300msec all day long.
So I think best choice we can do is that pass the decision to user by Kconfig which includes pointing the benchmark. I intionally removed "ARM" word in help because we checked the performance in just three devices of all ARM CPU so we can't make sure it does makse sense all ARM CPU.
Of course, I'm open for suggestion. Do you have better idea?
Quoted 10 lines
thanks,
greg k-h
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Signature · 8 lines
Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
Greg Kroah-Hartman
maintainerQuoted 69 lines · Minchan Kim
Hi Greg,
Quoted 52 lines · Greg Kroah-Hartman
Quoted 51 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +12
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmallocdrivers/staging/zsmalloc/zsmalloc-main.c +0
-0@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)Quoted 13 lines
drivers/staging/zsmalloc/zsmalloc-main.c struct zs_pool { · line 230
Quoted 10 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-10-/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here -* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif Did you test this? I don't see the new config value you added actually do anything in this code. Also, if I select it incorrectly on ARM, or
Quoted 1 line
*slaps self*
Ok, so I'll drop this patch now. As for what to do instead, I have no idea, sorry, but the others should.
thanks,
greg k-h
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Quoted 70 lines · Greg Kroah-Hartman
Quoted 69 lines · Minchan Kim
Hi Greg,
Quoted 65 lines · Greg Kroah-Hartman
Quoted 51 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +12
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmallocdrivers/staging/zsmalloc/zsmalloc-main.c +0
-0@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)drivers/staging/zsmalloc/zsmalloc-main.c struct zs_pool { · line 230
Quoted 10 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-10-/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here -* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif Did you test this? I don't see the new config value you added actually do anything in this code. Also, if I select it incorrectly on ARM, or
Quoted 4 lines
Quoted 1 line
*slaps self*
Ok, so I'll drop this patch now. As for what to do instead, I have no idea, sorry, but the others should.
Okay. Then, let's discuss further.
The history we introuced copy-based method is due to portability casused by set_pte and __flush_tlb_one usage in young zsmalloc age. They are gone now so there isn't issue any more. But we found copy-based method is 3 times faster than pte-based in VM so I expect you guys don't want to give up it for just portability. Of course,
I can't give up pte-based model as you know well, it's 6 times faster than copy-based model in ARM.
Hard-coding for some arch like now isn't good and Kconfig for selecting choice was rejected by Greg as you can see above.
Remained thing is new Kconfig ZSMALLOC_SMART_CHOICE and adding
new boot/module paramter. If admin enable it, In booting and module loading time, zsmalloc start benchmark both model, find best in the system and select it. If it is different with thing admin selected or default method, zsmalloc can warn about it so he can select right choice next time without enabling ZSMALLOC_SMART_CHOICE so he don't lose booting time and code size.
For it, we should add some code for benchamrk and selecting model dynamically. Frankly speaking, I feel it's overkill. zsmalloc is in staging now so IMHO, I don't see any problem in my patch.
Anyway, we should conclude agreeement and Andrew, too because he asked to add Kconfig model to promote zsmalloc.
Andrew, Nitin, Dan, Seth and Konrad?
What do you think about it?
Quoted 10 lines
thanks,
greg k-h
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Signature · 8 lines
Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
Greg Kroah-Hartman
maintainerQuoted 17 lines · Minchan Kim
Quoted 7 lines
Quoted 4 lines
Quoted 2 lines
Did you test this? I don't see the new config value you added actually do anything in this code. Also, if I select it incorrectly on ARM, or
*slaps self*
Ok, so I'll drop this patch now. As for what to do instead, I have no idea, sorry, but the others should.
Okay. Then, let's discuss further.
The history we introuced copy-based method is due to portability casused byset_pteand__flush_tlb_oneusage in young zsmalloc age. They are gone now so there isn't issue any more. But we found copy-based method is 3 times faster than pte-based in VM so I expect you guys don't want to give up it for just portability. Of course,
I can't give up pte-based model as you know well, it's 6 times faster than copy-based model in ARM.
Quoted 2 lines
Hard-coding for some arch like now isn't good and
Kconfigfor selecting choice was rejected by Greg as you can see above.
I rejected your patch because it did not do anything, why would I accept it?
What would you have done in my situation?
It's not an issue of "portability" or "speed" or anything other than "the patch you sent was obviously not correct."
greg k-h
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Hi Greg,
Quoted 21 lines · Greg Kroah-Hartman
Quoted 17 lines · Minchan Kim
Quoted 7 lines
Quoted 4 lines
Quoted 2 lines
Did you test this? I don't see the new config value you added actually do anything in this code. Also, if I select it incorrectly on ARM, or
*slaps self*
Ok, so I'll drop this patch now. As for what to do instead, I have no idea, sorry, but the others should.
Okay. Then, let's discuss further.
The history we introuced copy-based method is due to portability casused byset_pteand__flush_tlb_oneusage in young zsmalloc age. They are gone now so there isn't issue any more. But we found copy-based method is 3 times faster than pte-based in VM so I expect you guys don't want to give up it for just portability. Of course,
I can't give up pte-based model as you know well, it's 6 times faster than copy-based model in ARM.Quoted 2 lines
Hard-coding for some arch like now isn't good and
Kconfigfor selecting choice was rejected by Greg as you can see above.
Quoted 7 lines
I rejected your patch because it did not do anything, why would I accept it?
What would you have done in my situation?
It's not an issue of "portability" or "speed" or anything other than "the patch you sent was obviously not correct."
I totally misunderstood that you'd like to solve this issue. "Also, if I select it incorrectly on ARM, or
or other platforms, what is keeping this from doing bad things?" Then, I will resend it soon.
Thanks.
Quoted 8 lines
greg k-h
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Signature · 8 lines
Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
Quoted 33 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +2
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not a pointer, is returned by an alloc(). This handle must be mapped in order to access the allocated space. + +config ZSMALLOC_PGTABLE_MAPPING
drivers/staging/zsmalloc/Kconfig config ZSMALLOC · line 22
Quoted 10 lines
drivers/staging/zsmalloc/Kconfig +10
-0+ bool "Use page table mapping to access allocations that span two pages" + depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping method to access + allocations that span two pages. However, if a particular architecture + performs VM mapping faster than copying, then you should select this. + This causes zsmalloc to use page table mapping rather than copying + for object mapping. You can check speed with zsmalloc benchmark[1]. + [1] https://github.com/spartacus06/zsmalloc
Is there benchmark to test zcache? eg. internal fragmentation level ...
Quoted 12 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-4@@ -218,17 +218,6 @@ struct zs_pool {#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1) -/* -* By default, zsmalloc uses a copy-based object mapping method to access -* allocations that span two pages. However, if a particular architecture -* performs VM mapping faster than copying, then it should be added here
drivers/staging/zsmalloc/zsmalloc-main.c struct zs_pool { · line 223
Quoted 10 lines
drivers/staging/zsmalloc/zsmalloc-main.c +0
-7-* so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use -* page table mapping rather than copying for object mapping. -*/ -#if defined(CONFIG_ARM ) -#define USE_PGTABLE_MAPPING -#endif -struct mapping_area {#ifdef USE_PGTABLE_MAPPING struct vm_struct *vm;/* vm area for mapping object that span pages */
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Quoted 46 lines · Ric Mason
Quoted 45 lines · Minchan Kim
Zsmalloc has two methods 1) copy-based and 2) pte based to access allocations that span two pages.
You can see history why we supported two approach from [1].But it was bad choice that adding hard coding to select architecture which want to use pte based method. This patch removed it and adds new
Kconfigto select the approach.This patch is based on next-20130202.
[1] https://lkml.org/lkml/2012/7/11/58
Cc Andrew Morton <[email protected]>Cc Seth Jennings <[email protected]>Cc Nitin Gupta <[email protected]>Cc Dan Magenheimer <[email protected]>Cc Konrad Rzeszutek Wilk <[email protected]>Signed-off-by Minchan Kim <[email protected]>--- drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++ drivers/staging/zsmalloc/zsmalloc-main.c | 11 ----------- 2 files changed, 12 insertions(+), 11 deletions(-)drivers/staging/zsmalloc/Kconfig +0
-0@@ -8,3 +8,15 @@ config ZSMALLOC non-standard allocator interface where a handle, not apointer, is
returned by analloc(). This handle must be mapped in order to access the allocated space.drivers/staging/zsmalloc/Kconfig +3
-0+ +config ZSMALLOC_PGTABLE_MAPPING + bool "Use page table mapping to access allocations thatspan two pages"
drivers/staging/zsmalloc/Kconfig +4
-0+ depends on ZSMALLOC + default n + help + By default, zsmalloc uses a copy-based object mapping methodto access
+ allocations that span two pages. However, if a particular
architecture
+ performs VM mapping faster than copying, then you should
Quoted 8 lines
Quoted 6 lines
select this.
+ This causes zsmalloc to use page table mapping rather than
copying
+ for object mapping. You can check speed with zsmalloc
benchmark[1].
+ [1] https://github.com/spartacus06/zsmallocIs there benchmark to test zcache? eg. internal fragmentation level ...
First, zsmalloc is not used in zcache right now so just wanted to say that. It is used in zram and the proposed zswap
(https://lwn.net/Articles/528817/)
There is not an official benchmark. However anything that generates activity that will hit the frontswap or cleancache hooks will do. These are workloads that overcommit memory and use swap, or access file sets whose size is larger that the system page cache.
The closest thing to a fragmentation metric is an effective compression ratio that can be calculated with debugfs attributes:
zcache_[eph|pers]_zbytes / (zcache_[eph|pers]_pageframes * PAGE_SIZE)
eph for cleancache, and pers for frontswap.
Seth
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Quoted 11 lines
From: Seth Jennings [mailto:[email protected]]
Subject: Re: [PATCH] zsmalloc: AddKconfigfor enabling PTE methodQuoted 6 lines · Ric Mason
Quoted 3 lines · Minchan Kim
+ for object mapping. You can check speed with zsmalloc
benchmark[1].
+ [1] https://github.com/spartacus06/zsmallocIs there benchmark to test zcache? eg. internal fragmentation level ...
Quoted 8 lines
First, zsmalloc is not used in zcache right now so just wanted to say that. It is used in zram and the proposed zswap
(https://lwn.net/Articles/528817/)There is not an official benchmark. However anything that generates activity that will hit the frontswap or cleancache hooks will do. These are workloads that overcommit memory and use swap, or access file sets whose size is larger that the system page cache.
I think it's important to note that the question "is there a benchmark" is a very deep and difficult question for any compression solution because it is so workload-dependent. Unlike many benchmarks that simply synthesize a _quantity_ of data, zcache/zswap/zram all are very sensitive to the actual contents of that data as the compression ratio varies widely depending on the data. So we need to ensure that the data used by any benchmark has similar "entropy" to real world workloads. I'm not sure how we can do that.
So it may or may not be useful to measure zcache/zswap/zram using standard benchmarks (including things like SPECjbb). At least kernbench is something that kernel developers do every day, so it is definitely a real world workload... but adding parallel compiles (via "make -jN") until the system thrashes, and then showing zcache/zswap/zram reduces the thrashing may not be at all representative of a broad range of workloads that cause memory pressure... kernbench is just convenient for us developers to demonstrate that the mechanism works.
Ideas welcome... well-thought out ideas anyway!
Dan
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