* Re: [RFC] genalloc != generic DEVICE memory allocator
@ 2005-12-22 18:18 ` Andrey Volkov
0 siblings, 0 replies; 28+ messages in thread
From: Andrey Volkov @ 2005-12-22 18:18 UTC (permalink / raw)
To: Jes Sorensen, Pantelis Antoniou
Cc: linux-kernel, Andrew Morton, linuxppc-embedded
Hi Jes,
Jes Sorensen wrote:
>>>>>>"Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
>
>
> Andrey> Hello Jes and all I try to use your allocator (gen_pool_xxx),
> Andrey> idea of which is a cute nice thing. But current implementation
> Andrey> of it is inappropriate for a _device_ (aka onchip, like
> Andrey> framebuffer) memory allocation, by next reasons:
>
> Andrey,
>
> Keep in mind that genalloc was meant to be simple for basic memory
> allocations. It was never meant to be an over complex super high
> performance allocation mechanism.
>
> Andrey> 1) Device memory is expensive resource by access time and/or
> Andrey> size cost. So we couldn't use (usually) this memory for the
> Andrey> free blocks lists.
>
> This really is irrelevant, the space is only used within the object
> when it's on the free list. Ie. if all memory is handed out there's
> no space used for this purpose.
I point out 2 reasons: ACCESS TIME was first :), let take very
widespread case: PCI device with some onboard memory and any
N GHz proc. - result may be terrible: each access to device mem (which
usually uncached) will slowed down this super fast proc to 33 MHZ, i.e
same as we made busy-wait with disabled interrupts after each read/write...
I possible awry when use 'control structures' in 2), I've in view
allocator's control structures (size/next etc), not device specific
control structs.
>
> Andrey> 3) Obvious (IMHO) workflow of mem. allocator
> Andrey> look like: - at startup time, driver allocate some big
> Andrey> (almost) static mem. chunk(s) for a control/data structures.
> Andrey> - during work of the device, driver allocate many small
> Andrey> mem. blocks with almost identical size. such behavior lead to
> Andrey> degeneration of buddy method and transform it to the
> Andrey> first/best fit method (with long seek by the free node list).
>
> This is only really valid for network devices, and even then it's not
> quite so. For things like uncached allocations your observation is
> completely off.
Could you give me some examples? Possible I overlooked something
significant.
>
> For the case of more traditional devices, the control structures will
> be allocated from one end of the block, the rest will be used for
> packet descriptors which will be going in and out of the memory pool
> on a regular basis.
This was main reason why I try to modify genalloc: I needed in
generic allocator for both short-live strictly aligned blocks and
long-live blocks with restriction by size.
> In most normal cases these will all be of the same
> size and it doesn't matter where in the memory space they were
> allocated.
And thats also why I consider that 'buddy' is not appropriate to be
'generic' (most cases == generic, isn't is :)?): when you're allocate
mainly same sized blocks, 'buddy' degraded to the first-fit.
Possible solution I see in mixed first-fit with lazy coalescent for
short lived blocks and first-fit with immediately coalescent for
long-lived blocks. But, again, I may overlook something significant.
And, certainly, I could overlooked someone else allocator implementation
in some driver.
>
> Andrey> 4) The simple binary buddy method is far away from perfect for
> Andrey> a device due to a big internal fragmentation. Especially for a
> Andrey> network/mfd devices, for which, size of allocated data very
> Andrey> often is not a power of 2.
>
snip
>
> Andrey> I start to modify your code to satisfy above demands, but
> Andrey> firstly I wish to know your, or somebody else, opinion.
>
> I honestly don't think the majority of your demands are valid.
> genalloc was meant to be simple, not an ultra fast at any random
> block size allocator. So far I don't see any reason for changing to
> the allocation algorithm into anything much more complex - doesn't
> mean there couldn't be a reason for doing so, but I don't think you
> have described any so far.
I disagree here, generic couldn't be very simple and slow, because in
this case simply no one will be use it, and hence we'll get today's
picture: reimplemented allocators in many drivers.
>
> You mentioned frame buffers, but what is the kernel supposed to do
> with those allocation wise? If you have a frame buffer console, the
> memory is allocated once and handed to the frame buffer driver.
> Ie. you don't need a ton of on demand allocations for that and for
> X, the memory management is handled in the X server, not by the
> kernel.
For video-only device this is true, but if device is a multifunctional,
which is frequent case in embedded systems, then kernel must control of
device memory allocation. Currently, however, even video cards for
desktops become more and more multifunctional (VIVO/audio etc.).
>
> The only thing I think would make sense to implement is to allow it to
> use indirect descriptor blocks for the memory it manages. This is not
> because it's wrong to use the memory for the free list, as it will
> only be used for this when the chunk is not in use, but because access
> to certain types of memory isn't always valid through normal direct
> access. Ie. if one used descriptor blocks residing in normal
> GFP_KERNEL memory, it would be possible to use the allocator to manage
> memory sitting on the other side of a PCI bus.
I describe above, why we couldn't/wouldn't use onboard memory for
allocator specific data.
Pantelis, Am I answered to your question (...what are you trying to
do...) too?
--
Regards
Andrey Volkov
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
2005-12-22 18:18 ` Andrey Volkov
@ 2005-12-22 18:33 ` Pantelis Antoniou
-1 siblings, 0 replies; 28+ messages in thread
From: Pantelis Antoniou @ 2005-12-22 18:33 UTC (permalink / raw)
To: linuxppc-embedded; +Cc: Andrew Morton, Jes Sorensen, linux-kernel
On Thursday 22 December 2005 20:18, Andrey Volkov wrote:
> Hi Jes,
>
> Jes Sorensen wrote:
> >>>>>>"Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
> >
> >
> > Andrey> Hello Jes and all I try to use your allocator (gen_pool_xxx),
> > Andrey> idea of which is a cute nice thing. But current implementation
> > Andrey> of it is inappropriate for a _device_ (aka onchip, like
> > Andrey> framebuffer) memory allocation, by next reasons:
> >
> > Andrey,
> >
> > Keep in mind that genalloc was meant to be simple for basic memory
> > allocations. It was never meant to be an over complex super high
> > performance allocation mechanism.
> >
> > Andrey> 1) Device memory is expensive resource by access time and/or
> > Andrey> size cost. So we couldn't use (usually) this memory for the
> > Andrey> free blocks lists.
> >
> > This really is irrelevant, the space is only used within the object
> > when it's on the free list. Ie. if all memory is handed out there's
> > no space used for this purpose.
>
> I point out 2 reasons: ACCESS TIME was first :), let take very
> widespread case: PCI device with some onboard memory and any
> N GHz proc. - result may be terrible: each access to device mem (which
> usually uncached) will slowed down this super fast proc to 33 MHZ, i.e
> same as we made busy-wait with disabled interrupts after each read/write...
>
> I possible awry when use 'control structures' in 2), I've in view
> allocator's control structures (size/next etc), not device specific
> control structs.
>
> >
> > Andrey> 3) Obvious (IMHO) workflow of mem. allocator
> > Andrey> look like: - at startup time, driver allocate some big
> > Andrey> (almost) static mem. chunk(s) for a control/data structures.
> > Andrey> - during work of the device, driver allocate many small
> > Andrey> mem. blocks with almost identical size. such behavior lead to
> > Andrey> degeneration of buddy method and transform it to the
> > Andrey> first/best fit method (with long seek by the free node list).
> >
> > This is only really valid for network devices, and even then it's not
> > quite so. For things like uncached allocations your observation is
> > completely off.
>
> Could you give me some examples? Possible I overlooked something
> significant.
>
> >
> > For the case of more traditional devices, the control structures will
> > be allocated from one end of the block, the rest will be used for
> > packet descriptors which will be going in and out of the memory pool
> > on a regular basis.
>
> This was main reason why I try to modify genalloc: I needed in
> generic allocator for both short-live strictly aligned blocks and
> long-live blocks with restriction by size.
>
> > In most normal cases these will all be of the same
> > size and it doesn't matter where in the memory space they were
> > allocated.
>
> And thats also why I consider that 'buddy' is not appropriate to be
> 'generic' (most cases == generic, isn't is :)?): when you're allocate
> mainly same sized blocks, 'buddy' degraded to the first-fit.
>
> Possible solution I see in mixed first-fit with lazy coalescent for
> short lived blocks and first-fit with immediately coalescent for
> long-lived blocks. But, again, I may overlook something significant.
> And, certainly, I could overlooked someone else allocator implementation
> in some driver.
>
> >
> > Andrey> 4) The simple binary buddy method is far away from perfect for
> > Andrey> a device due to a big internal fragmentation. Especially for a
> > Andrey> network/mfd devices, for which, size of allocated data very
> > Andrey> often is not a power of 2.
> >
> snip
> >
> > Andrey> I start to modify your code to satisfy above demands, but
> > Andrey> firstly I wish to know your, or somebody else, opinion.
> >
> > I honestly don't think the majority of your demands are valid.
> > genalloc was meant to be simple, not an ultra fast at any random
> > block size allocator. So far I don't see any reason for changing to
> > the allocation algorithm into anything much more complex - doesn't
> > mean there couldn't be a reason for doing so, but I don't think you
> > have described any so far.
> I disagree here, generic couldn't be very simple and slow, because in
> this case simply no one will be use it, and hence we'll get today's
> picture: reimplemented allocators in many drivers.
>
> >
> > You mentioned frame buffers, but what is the kernel supposed to do
> > with those allocation wise? If you have a frame buffer console, the
> > memory is allocated once and handed to the frame buffer driver.
> > Ie. you don't need a ton of on demand allocations for that and for
> > X, the memory management is handled in the X server, not by the
> > kernel.
>
> For video-only device this is true, but if device is a multifunctional,
> which is frequent case in embedded systems, then kernel must control of
> device memory allocation. Currently, however, even video cards for
> desktops become more and more multifunctional (VIVO/audio etc.).
>
> >
> > The only thing I think would make sense to implement is to allow it to
> > use indirect descriptor blocks for the memory it manages. This is not
> > because it's wrong to use the memory for the free list, as it will
> > only be used for this when the chunk is not in use, but because access
> > to certain types of memory isn't always valid through normal direct
> > access. Ie. if one used descriptor blocks residing in normal
> > GFP_KERNEL memory, it would be possible to use the allocator to manage
> > memory sitting on the other side of a PCI bus.
> I describe above, why we couldn't/wouldn't use onboard memory for
> allocator specific data.
>
> Pantelis, Am I answered to your question (...what are you trying to
> do...) too?
>
Yes. rheap seems to cover your cases...
> --
> Regards
> Andrey Volkov
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>
Regards
Pantelis
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
@ 2005-12-22 18:33 ` Pantelis Antoniou
0 siblings, 0 replies; 28+ messages in thread
From: Pantelis Antoniou @ 2005-12-22 18:33 UTC (permalink / raw)
To: linuxppc-embedded
Cc: Andrey Volkov, Jes Sorensen, Pantelis Antoniou, Andrew Morton,
linux-kernel
On Thursday 22 December 2005 20:18, Andrey Volkov wrote:
> Hi Jes,
>
> Jes Sorensen wrote:
> >>>>>>"Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
> >
> >
> > Andrey> Hello Jes and all I try to use your allocator (gen_pool_xxx),
> > Andrey> idea of which is a cute nice thing. But current implementation
> > Andrey> of it is inappropriate for a _device_ (aka onchip, like
> > Andrey> framebuffer) memory allocation, by next reasons:
> >
> > Andrey,
> >
> > Keep in mind that genalloc was meant to be simple for basic memory
> > allocations. It was never meant to be an over complex super high
> > performance allocation mechanism.
> >
> > Andrey> 1) Device memory is expensive resource by access time and/or
> > Andrey> size cost. So we couldn't use (usually) this memory for the
> > Andrey> free blocks lists.
> >
> > This really is irrelevant, the space is only used within the object
> > when it's on the free list. Ie. if all memory is handed out there's
> > no space used for this purpose.
>
> I point out 2 reasons: ACCESS TIME was first :), let take very
> widespread case: PCI device with some onboard memory and any
> N GHz proc. - result may be terrible: each access to device mem (which
> usually uncached) will slowed down this super fast proc to 33 MHZ, i.e
> same as we made busy-wait with disabled interrupts after each read/write...
>
> I possible awry when use 'control structures' in 2), I've in view
> allocator's control structures (size/next etc), not device specific
> control structs.
>
> >
> > Andrey> 3) Obvious (IMHO) workflow of mem. allocator
> > Andrey> look like: - at startup time, driver allocate some big
> > Andrey> (almost) static mem. chunk(s) for a control/data structures.
> > Andrey> - during work of the device, driver allocate many small
> > Andrey> mem. blocks with almost identical size. such behavior lead to
> > Andrey> degeneration of buddy method and transform it to the
> > Andrey> first/best fit method (with long seek by the free node list).
> >
> > This is only really valid for network devices, and even then it's not
> > quite so. For things like uncached allocations your observation is
> > completely off.
>
> Could you give me some examples? Possible I overlooked something
> significant.
>
> >
> > For the case of more traditional devices, the control structures will
> > be allocated from one end of the block, the rest will be used for
> > packet descriptors which will be going in and out of the memory pool
> > on a regular basis.
>
> This was main reason why I try to modify genalloc: I needed in
> generic allocator for both short-live strictly aligned blocks and
> long-live blocks with restriction by size.
>
> > In most normal cases these will all be of the same
> > size and it doesn't matter where in the memory space they were
> > allocated.
>
> And thats also why I consider that 'buddy' is not appropriate to be
> 'generic' (most cases == generic, isn't is :)?): when you're allocate
> mainly same sized blocks, 'buddy' degraded to the first-fit.
>
> Possible solution I see in mixed first-fit with lazy coalescent for
> short lived blocks and first-fit with immediately coalescent for
> long-lived blocks. But, again, I may overlook something significant.
> And, certainly, I could overlooked someone else allocator implementation
> in some driver.
>
> >
> > Andrey> 4) The simple binary buddy method is far away from perfect for
> > Andrey> a device due to a big internal fragmentation. Especially for a
> > Andrey> network/mfd devices, for which, size of allocated data very
> > Andrey> often is not a power of 2.
> >
> snip
> >
> > Andrey> I start to modify your code to satisfy above demands, but
> > Andrey> firstly I wish to know your, or somebody else, opinion.
> >
> > I honestly don't think the majority of your demands are valid.
> > genalloc was meant to be simple, not an ultra fast at any random
> > block size allocator. So far I don't see any reason for changing to
> > the allocation algorithm into anything much more complex - doesn't
> > mean there couldn't be a reason for doing so, but I don't think you
> > have described any so far.
> I disagree here, generic couldn't be very simple and slow, because in
> this case simply no one will be use it, and hence we'll get today's
> picture: reimplemented allocators in many drivers.
>
> >
> > You mentioned frame buffers, but what is the kernel supposed to do
> > with those allocation wise? If you have a frame buffer console, the
> > memory is allocated once and handed to the frame buffer driver.
> > Ie. you don't need a ton of on demand allocations for that and for
> > X, the memory management is handled in the X server, not by the
> > kernel.
>
> For video-only device this is true, but if device is a multifunctional,
> which is frequent case in embedded systems, then kernel must control of
> device memory allocation. Currently, however, even video cards for
> desktops become more and more multifunctional (VIVO/audio etc.).
>
> >
> > The only thing I think would make sense to implement is to allow it to
> > use indirect descriptor blocks for the memory it manages. This is not
> > because it's wrong to use the memory for the free list, as it will
> > only be used for this when the chunk is not in use, but because access
> > to certain types of memory isn't always valid through normal direct
> > access. Ie. if one used descriptor blocks residing in normal
> > GFP_KERNEL memory, it would be possible to use the allocator to manage
> > memory sitting on the other side of a PCI bus.
> I describe above, why we couldn't/wouldn't use onboard memory for
> allocator specific data.
>
> Pantelis, Am I answered to your question (...what are you trying to
> do...) too?
>
Yes. rheap seems to cover your cases...
> --
> Regards
> Andrey Volkov
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>
Regards
Pantelis
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
2005-12-22 18:33 ` Pantelis Antoniou
@ 2005-12-23 7:38 ` Andrey Volkov
-1 siblings, 0 replies; 28+ messages in thread
From: Andrey Volkov @ 2005-12-23 7:38 UTC (permalink / raw)
To: pantelis.antoniou
Cc: Andrew Morton, Jes Sorensen, linux-kernel, linuxppc-embedded
Pantelis Antoniou wrote:
> On Thursday 22 December 2005 20:18, Andrey Volkov wrote:
>
>>Hi Jes,
>>
>>Jes Sorensen wrote:
>>
>>>>>>>>"Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
>>>
>>>
>>>Andrey> Hello Jes and all I try to use your allocator (gen_pool_xxx),
>>>Andrey> idea of which is a cute nice thing. But current implementation
>>>Andrey> of it is inappropriate for a _device_ (aka onchip, like
>>>Andrey> framebuffer) memory allocation, by next reasons:
>>>
>>>Andrey,
>>>
>>>Keep in mind that genalloc was meant to be simple for basic memory
>>>allocations. It was never meant to be an over complex super high
>>>performance allocation mechanism.
>>>
>>>Andrey> 1) Device memory is expensive resource by access time and/or
>>>Andrey> size cost. So we couldn't use (usually) this memory for the
>>>Andrey> free blocks lists.
>>>
>>>This really is irrelevant, the space is only used within the object
>>>when it's on the free list. Ie. if all memory is handed out there's
>>>no space used for this purpose.
>>
>>I point out 2 reasons: ACCESS TIME was first :), let take very
>>widespread case: PCI device with some onboard memory and any
>>N GHz proc. - result may be terrible: each access to device mem (which
>>usually uncached) will slowed down this super fast proc to 33 MHZ, i.e
>>same as we made busy-wait with disabled interrupts after each read/write...
>>
>>I possible awry when use 'control structures' in 2), I've in view
>>allocator's control structures (size/next etc), not device specific
>>control structs.
>>
>>
>>>Andrey> 3) Obvious (IMHO) workflow of mem. allocator
>>>Andrey> look like: - at startup time, driver allocate some big
>>>Andrey> (almost) static mem. chunk(s) for a control/data structures.
>>>Andrey> - during work of the device, driver allocate many small
>>>Andrey> mem. blocks with almost identical size. such behavior lead to
>>>Andrey> degeneration of buddy method and transform it to the
>>>Andrey> first/best fit method (with long seek by the free node list).
>>>
>>>This is only really valid for network devices, and even then it's not
>>>quite so. For things like uncached allocations your observation is
>>>completely off.
>>
>>Could you give me some examples? Possible I overlooked something
>>significant.
>>
>>
>>>For the case of more traditional devices, the control structures will
>>>be allocated from one end of the block, the rest will be used for
>>>packet descriptors which will be going in and out of the memory pool
>>>on a regular basis.
>>
>>This was main reason why I try to modify genalloc: I needed in
>>generic allocator for both short-live strictly aligned blocks and
>>long-live blocks with restriction by size.
>>
>>
>>>In most normal cases these will all be of the same
>>>size and it doesn't matter where in the memory space they were
>>>allocated.
>>
>>And thats also why I consider that 'buddy' is not appropriate to be
>>'generic' (most cases == generic, isn't is :)?): when you're allocate
>>mainly same sized blocks, 'buddy' degraded to the first-fit.
>>
>>Possible solution I see in mixed first-fit with lazy coalescent for
>>short lived blocks and first-fit with immediately coalescent for
>>long-lived blocks. But, again, I may overlook something significant.
>>And, certainly, I could overlooked someone else allocator implementation
>>in some driver.
>>
>>
>>>Andrey> 4) The simple binary buddy method is far away from perfect for
>>>Andrey> a device due to a big internal fragmentation. Especially for a
>>>Andrey> network/mfd devices, for which, size of allocated data very
>>>Andrey> often is not a power of 2.
>>>
>>
>>snip
>>
>>>Andrey> I start to modify your code to satisfy above demands, but
>>>Andrey> firstly I wish to know your, or somebody else, opinion.
>>>
>>>I honestly don't think the majority of your demands are valid.
>>>genalloc was meant to be simple, not an ultra fast at any random
>>>block size allocator. So far I don't see any reason for changing to
>>>the allocation algorithm into anything much more complex - doesn't
>>>mean there couldn't be a reason for doing so, but I don't think you
>>>have described any so far.
>>
>>I disagree here, generic couldn't be very simple and slow, because in
>>this case simply no one will be use it, and hence we'll get today's
>>picture: reimplemented allocators in many drivers.
>>
>>
>>>You mentioned frame buffers, but what is the kernel supposed to do
>>>with those allocation wise? If you have a frame buffer console, the
>>>memory is allocated once and handed to the frame buffer driver.
>>>Ie. you don't need a ton of on demand allocations for that and for
>>>X, the memory management is handled in the X server, not by the
>>>kernel.
>>
>>For video-only device this is true, but if device is a multifunctional,
>>which is frequent case in embedded systems, then kernel must control of
>>device memory allocation. Currently, however, even video cards for
>>desktops become more and more multifunctional (VIVO/audio etc.).
>>
>>
>>>The only thing I think would make sense to implement is to allow it to
>>>use indirect descriptor blocks for the memory it manages. This is not
>>>because it's wrong to use the memory for the free list, as it will
>>>only be used for this when the chunk is not in use, but because access
>>>to certain types of memory isn't always valid through normal direct
>>>access. Ie. if one used descriptor blocks residing in normal
>>>GFP_KERNEL memory, it would be possible to use the allocator to manage
>>>memory sitting on the other side of a PCI bus.
>>
>>I describe above, why we couldn't/wouldn't use onboard memory for
>>allocator specific data.
>>
>>Pantelis, Am I answered to your question (...what are you trying to
>>do...) too?
>>
>
>
> Yes. rheap seems to cover your cases...
>
Agree, I couldn't see nothing better for a basement of generic dev. alloc.
So, it will be much better if it will be moved to lib/.
Anyone have some more comments about subj. ?
--
Regards
Andrey Volkov
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
@ 2005-12-23 7:38 ` Andrey Volkov
0 siblings, 0 replies; 28+ messages in thread
From: Andrey Volkov @ 2005-12-23 7:38 UTC (permalink / raw)
To: pantelis.antoniou
Cc: linuxppc-embedded, Jes Sorensen, Pantelis Antoniou, Andrew Morton,
linux-kernel
Pantelis Antoniou wrote:
> On Thursday 22 December 2005 20:18, Andrey Volkov wrote:
>
>>Hi Jes,
>>
>>Jes Sorensen wrote:
>>
>>>>>>>>"Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
>>>
>>>
>>>Andrey> Hello Jes and all I try to use your allocator (gen_pool_xxx),
>>>Andrey> idea of which is a cute nice thing. But current implementation
>>>Andrey> of it is inappropriate for a _device_ (aka onchip, like
>>>Andrey> framebuffer) memory allocation, by next reasons:
>>>
>>>Andrey,
>>>
>>>Keep in mind that genalloc was meant to be simple for basic memory
>>>allocations. It was never meant to be an over complex super high
>>>performance allocation mechanism.
>>>
>>>Andrey> 1) Device memory is expensive resource by access time and/or
>>>Andrey> size cost. So we couldn't use (usually) this memory for the
>>>Andrey> free blocks lists.
>>>
>>>This really is irrelevant, the space is only used within the object
>>>when it's on the free list. Ie. if all memory is handed out there's
>>>no space used for this purpose.
>>
>>I point out 2 reasons: ACCESS TIME was first :), let take very
>>widespread case: PCI device with some onboard memory and any
>>N GHz proc. - result may be terrible: each access to device mem (which
>>usually uncached) will slowed down this super fast proc to 33 MHZ, i.e
>>same as we made busy-wait with disabled interrupts after each read/write...
>>
>>I possible awry when use 'control structures' in 2), I've in view
>>allocator's control structures (size/next etc), not device specific
>>control structs.
>>
>>
>>>Andrey> 3) Obvious (IMHO) workflow of mem. allocator
>>>Andrey> look like: - at startup time, driver allocate some big
>>>Andrey> (almost) static mem. chunk(s) for a control/data structures.
>>>Andrey> - during work of the device, driver allocate many small
>>>Andrey> mem. blocks with almost identical size. such behavior lead to
>>>Andrey> degeneration of buddy method and transform it to the
>>>Andrey> first/best fit method (with long seek by the free node list).
>>>
>>>This is only really valid for network devices, and even then it's not
>>>quite so. For things like uncached allocations your observation is
>>>completely off.
>>
>>Could you give me some examples? Possible I overlooked something
>>significant.
>>
>>
>>>For the case of more traditional devices, the control structures will
>>>be allocated from one end of the block, the rest will be used for
>>>packet descriptors which will be going in and out of the memory pool
>>>on a regular basis.
>>
>>This was main reason why I try to modify genalloc: I needed in
>>generic allocator for both short-live strictly aligned blocks and
>>long-live blocks with restriction by size.
>>
>>
>>>In most normal cases these will all be of the same
>>>size and it doesn't matter where in the memory space they were
>>>allocated.
>>
>>And thats also why I consider that 'buddy' is not appropriate to be
>>'generic' (most cases == generic, isn't is :)?): when you're allocate
>>mainly same sized blocks, 'buddy' degraded to the first-fit.
>>
>>Possible solution I see in mixed first-fit with lazy coalescent for
>>short lived blocks and first-fit with immediately coalescent for
>>long-lived blocks. But, again, I may overlook something significant.
>>And, certainly, I could overlooked someone else allocator implementation
>>in some driver.
>>
>>
>>>Andrey> 4) The simple binary buddy method is far away from perfect for
>>>Andrey> a device due to a big internal fragmentation. Especially for a
>>>Andrey> network/mfd devices, for which, size of allocated data very
>>>Andrey> often is not a power of 2.
>>>
>>
>>snip
>>
>>>Andrey> I start to modify your code to satisfy above demands, but
>>>Andrey> firstly I wish to know your, or somebody else, opinion.
>>>
>>>I honestly don't think the majority of your demands are valid.
>>>genalloc was meant to be simple, not an ultra fast at any random
>>>block size allocator. So far I don't see any reason for changing to
>>>the allocation algorithm into anything much more complex - doesn't
>>>mean there couldn't be a reason for doing so, but I don't think you
>>>have described any so far.
>>
>>I disagree here, generic couldn't be very simple and slow, because in
>>this case simply no one will be use it, and hence we'll get today's
>>picture: reimplemented allocators in many drivers.
>>
>>
>>>You mentioned frame buffers, but what is the kernel supposed to do
>>>with those allocation wise? If you have a frame buffer console, the
>>>memory is allocated once and handed to the frame buffer driver.
>>>Ie. you don't need a ton of on demand allocations for that and for
>>>X, the memory management is handled in the X server, not by the
>>>kernel.
>>
>>For video-only device this is true, but if device is a multifunctional,
>>which is frequent case in embedded systems, then kernel must control of
>>device memory allocation. Currently, however, even video cards for
>>desktops become more and more multifunctional (VIVO/audio etc.).
>>
>>
>>>The only thing I think would make sense to implement is to allow it to
>>>use indirect descriptor blocks for the memory it manages. This is not
>>>because it's wrong to use the memory for the free list, as it will
>>>only be used for this when the chunk is not in use, but because access
>>>to certain types of memory isn't always valid through normal direct
>>>access. Ie. if one used descriptor blocks residing in normal
>>>GFP_KERNEL memory, it would be possible to use the allocator to manage
>>>memory sitting on the other side of a PCI bus.
>>
>>I describe above, why we couldn't/wouldn't use onboard memory for
>>allocator specific data.
>>
>>Pantelis, Am I answered to your question (...what are you trying to
>>do...) too?
>>
>
>
> Yes. rheap seems to cover your cases...
>
Agree, I couldn't see nothing better for a basement of generic dev. alloc.
So, it will be much better if it will be moved to lib/.
Anyone have some more comments about subj. ?
--
Regards
Andrey Volkov
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
2005-12-23 7:38 ` Andrey Volkov
@ 2005-12-23 7:46 ` Pantelis Antoniou
-1 siblings, 0 replies; 28+ messages in thread
From: Pantelis Antoniou @ 2005-12-23 7:46 UTC (permalink / raw)
To: Andrey Volkov
Cc: Andrew Morton, Jes Sorensen, linuxppc-embedded, linux-kernel
>
[snip]
>
> Agree, I couldn't see nothing better for a basement of generic dev. alloc.
>
> So, it will be much better if it will be moved to lib/.
>
> Anyone have some more comments about subj. ?
>
Sure, but the call has to be made be a core developer.
Andrew?
Regards
Pantelis
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
@ 2005-12-23 7:46 ` Pantelis Antoniou
0 siblings, 0 replies; 28+ messages in thread
From: Pantelis Antoniou @ 2005-12-23 7:46 UTC (permalink / raw)
To: Andrey Volkov
Cc: pantelis.antoniou, linuxppc-embedded, Jes Sorensen, Andrew Morton,
linux-kernel
>
[snip]
>
> Agree, I couldn't see nothing better for a basement of generic dev. alloc.
>
> So, it will be much better if it will be moved to lib/.
>
> Anyone have some more comments about subj. ?
>
Sure, but the call has to be made be a core developer.
Andrew?
Regards
Pantelis
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
2005-12-23 7:46 ` Pantelis Antoniou
@ 2005-12-23 10:17 ` Andrey Volkov
-1 siblings, 0 replies; 28+ messages in thread
From: Andrey Volkov @ 2005-12-23 10:17 UTC (permalink / raw)
To: Pantelis Antoniou
Cc: Andrew Morton, Jes Sorensen, linuxppc-embedded, linux-kernel
Pantelis Antoniou wrote:
>>
>
> [snip]
>
>>
>> Agree, I couldn't see nothing better for a basement of generic dev.
>> alloc.
>>
>> So, it will be much better if it will be moved to lib/.
>>
>> Anyone have some more comments about subj. ?
>>
>
> Sure, but the call has to be made be a core developer.
>
> Andrew?
Pantelis, what did you think about renaming rheap.c and rh_xxx, to
something like dev_xxx, since, for example, rh_alloc overlapped with
__rh_alloc (__RegionHach__alloc) in the drivers/md/dm-raid1.c.
--
Regards
Andrey Volkov
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
@ 2005-12-23 10:17 ` Andrey Volkov
0 siblings, 0 replies; 28+ messages in thread
From: Andrey Volkov @ 2005-12-23 10:17 UTC (permalink / raw)
To: Pantelis Antoniou
Cc: pantelis.antoniou, linuxppc-embedded, Jes Sorensen, Andrew Morton,
linux-kernel
Pantelis Antoniou wrote:
>>
>
> [snip]
>
>>
>> Agree, I couldn't see nothing better for a basement of generic dev.
>> alloc.
>>
>> So, it will be much better if it will be moved to lib/.
>>
>> Anyone have some more comments about subj. ?
>>
>
> Sure, but the call has to be made be a core developer.
>
> Andrew?
Pantelis, what did you think about renaming rheap.c and rh_xxx, to
something like dev_xxx, since, for example, rh_alloc overlapped with
__rh_alloc (__RegionHach__alloc) in the drivers/md/dm-raid1.c.
--
Regards
Andrey Volkov
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
2005-12-22 18:18 ` Andrey Volkov
@ 2005-12-23 10:59 ` Jes Sorensen
-1 siblings, 0 replies; 28+ messages in thread
From: Jes Sorensen @ 2005-12-23 10:59 UTC (permalink / raw)
To: Andrey Volkov; +Cc: Andrew Morton, linux-kernel, linuxppc-embedded
>>>>> "Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
Andrey> Hi Jes,
Andrey> Jes Sorensen wrote:
>> This really is irrelevant, the space is only used within the
>> object when it's on the free list. Ie. if all memory is handed out
>> there's no space used for this purpose.
Andrey> I point out 2 reasons: ACCESS TIME was first :), let take very
Andrey> widespread case: PCI device with some onboard memory and any N
Andrey> GHz proc. - result may be terrible: each access to device mem
Andrey> (which usually uncached) will slowed down this super fast proc
Andrey> to 33 MHZ, i.e same as we made busy-wait with disabled
Andrey> interrupts after each read/write...
Andrey,
As I said in my response, you need the control blocks because you are
not allowed to directly access things on the other side of the PCI bus
without using the readl/writel equivalent macros. It's got nothing to
do with access speed.
>> For the case of more traditional devices, the control structures
>> will be allocated from one end of the block, the rest will be used
>> for packet descriptors which will be going in and out of the memory
>> pool on a regular basis.
Andrey> This was main reason why I try to modify genalloc: I needed in
Andrey> generic allocator for both short-live strictly aligned blocks
Andrey> and long-live blocks with restriction by size.
genalloc is perfectly adequate for that purpose. The long lived
allocations will just be taken out first, the rest will be used for
the short lived.
>> In most normal cases these will all be of the same size and it
>> doesn't matter where in the memory space they were allocated.
Andrey> And thats also why I consider that 'buddy' is not appropriate
Andrey> to be 'generic' (most cases == generic, isn't is :)?): when
Andrey> you're allocate mainly same sized blocks, 'buddy' degraded to
Andrey> the first-fit.
huh?
>> I honestly don't think the majority of your demands are valid.
>> genalloc was meant to be simple, not an ultra fast at any random
>> block size allocator. So far I don't see any reason for changing to
>> the allocation algorithm into anything much more complex - doesn't
>> mean there couldn't be a reason for doing so, but I don't think you
>> have described any so far.
Andrey> I disagree here, generic couldn't be very simple and slow,
Andrey> because in this case simply no one will be use it, and hence
Andrey> we'll get today's picture: reimplemented allocators in many
Andrey> drivers.
Of course it can. I will continue to claim that you are trying to turn
it into something it doesn't need to be. The allocator I used was
based on the allocator from the old sym2 driver, which is a perfect
example of it being used by a device driver.
>> You mentioned frame buffers, but what is the kernel supposed to do
>> with those allocation wise? If you have a frame buffer console, the
>> memory is allocated once and handed to the frame buffer driver.
>> Ie. you don't need a ton of on demand allocations for that and for
>> X, the memory management is handled in the X server, not by the
>> kernel.
Andrey> For video-only device this is true, but if device is a
Andrey> multifunctional, which is frequent case in embedded systems,
Andrey> then kernel must control of device memory
Andrey> allocation. Currently, however, even video cards for desktops
Andrey> become more and more multifunctional (VIVO/audio etc.).
For multi functional devices you still often split the memory up at
init time. Some memory is never going to be given back (like the frame
buffer itself), other blocks are like the network packet descriptors
in a network device.
>> The only thing I think would make sense to implement is to allow
>> it to use indirect descriptor blocks for the memory it
>> manages. This is not because it's wrong to use the memory for the
>> free list, as it will only be used for this when the chunk is not
>> in use, but because access to certain types of memory isn't always
>> valid through normal direct access. Ie. if one used descriptor
>> blocks residing in normal GFP_KERNEL memory, it would be possible
>> to use the allocator to manage memory sitting on the other side of
>> a PCI bus.
Andrey> I describe above, why we couldn't/wouldn't use onboard memory
Andrey> for allocator specific data.
As I pointed out, your description wasn't valid. You are not allowed
to directly dereference memory on the other side of a PCI bus.
Regards,
Jes
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC] genalloc != generic DEVICE memory allocator
@ 2005-12-23 10:59 ` Jes Sorensen
0 siblings, 0 replies; 28+ messages in thread
From: Jes Sorensen @ 2005-12-23 10:59 UTC (permalink / raw)
To: Andrey Volkov
Cc: Pantelis Antoniou, linux-kernel, Andrew Morton, linuxppc-embedded
>>>>> "Andrey" == Andrey Volkov <avolkov@varma-el.com> writes:
Andrey> Hi Jes,
Andrey> Jes Sorensen wrote:
>> This really is irrelevant, the space is only used within the
>> object when it's on the free list. Ie. if all memory is handed out
>> there's no space used for this purpose.
Andrey> I point out 2 reasons: ACCESS TIME was first :), let take very
Andrey> widespread case: PCI device with some onboard memory and any N
Andrey> GHz proc. - result may be terrible: each access to device mem
Andrey> (which usually uncached) will slowed down this super fast proc
Andrey> to 33 MHZ, i.e same as we made busy-wait with disabled
Andrey> interrupts after each read/write...
Andrey,
As I said in my response, you need the control blocks because you are
not allowed to directly access things on the other side of the PCI bus
without using the readl/writel equivalent macros. It's got nothing to
do with access speed.
>> For the case of more traditional devices, the control structures
>> will be allocated from one end of the block, the rest will be used
>> for packet descriptors which will be going in and out of the memory
>> pool on a regular basis.
Andrey> This was main reason why I try to modify genalloc: I needed in
Andrey> generic allocator for both short-live strictly aligned blocks
Andrey> and long-live blocks with restriction by size.
genalloc is perfectly adequate for that purpose. The long lived
allocations will just be taken out first, the rest will be used for
the short lived.
>> In most normal cases these will all be of the same size and it
>> doesn't matter where in the memory space they were allocated.
Andrey> And thats also why I consider that 'buddy' is not appropriate
Andrey> to be 'generic' (most cases == generic, isn't is :)?): when
Andrey> you're allocate mainly same sized blocks, 'buddy' degraded to
Andrey> the first-fit.
huh?
>> I honestly don't think the majority of your demands are valid.
>> genalloc was meant to be simple, not an ultra fast at any random
>> block size allocator. So far I don't see any reason for changing to
>> the allocation algorithm into anything much more complex - doesn't
>> mean there couldn't be a reason for doing so, but I don't think you
>> have described any so far.
Andrey> I disagree here, generic couldn't be very simple and slow,
Andrey> because in this case simply no one will be use it, and hence
Andrey> we'll get today's picture: reimplemented allocators in many
Andrey> drivers.
Of course it can. I will continue to claim that you are trying to turn
it into something it doesn't need to be. The allocator I used was
based on the allocator from the old sym2 driver, which is a perfect
example of it being used by a device driver.
>> You mentioned frame buffers, but what is the kernel supposed to do
>> with those allocation wise? If you have a frame buffer console, the
>> memory is allocated once and handed to the frame buffer driver.
>> Ie. you don't need a ton of on demand allocations for that and for
>> X, the memory management is handled in the X server, not by the
>> kernel.
Andrey> For video-only device this is true, but if device is a
Andrey> multifunctional, which is frequent case in embedded systems,
Andrey> then kernel must control of device memory
Andrey> allocation. Currently, however, even video cards for desktops
Andrey> become more and more multifunctional (VIVO/audio etc.).
For multi functional devices you still often split the memory up at
init time. Some memory is never going to be given back (like the frame
buffer itself), other blocks are like the network packet descriptors
in a network device.
>> The only thing I think would make sense to implement is to allow
>> it to use indirect descriptor blocks for the memory it
>> manages. This is not because it's wrong to use the memory for the
>> free list, as it will only be used for this when the chunk is not
>> in use, but because access to certain types of memory isn't always
>> valid through normal direct access. Ie. if one used descriptor
>> blocks residing in normal GFP_KERNEL memory, it would be possible
>> to use the allocator to manage memory sitting on the other side of
>> a PCI bus.
Andrey> I describe above, why we couldn't/wouldn't use onboard memory
Andrey> for allocator specific data.
As I pointed out, your description wasn't valid. You are not allowed
to directly dereference memory on the other side of a PCI bus.
Regards,
Jes
^ permalink raw reply [flat|nested] 28+ messages in thread