[9fans] Sam arena allocators

[9fans] Sam arena allocators

[silas poulson]

Hi,

Recently discovered a blog post[1] stating Sam used to have arena
based allocators.

Having difficulty finding more about this - does anyone know what the
allocator looked like and why the source returned to using the
standard allocators.

Silas

[1]https://jeremywsherman.com/2012/02/28/memory-allocation-in-sam/


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Re: [9fans] Sam arena allocators

[Rob Pike]

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After Acme was written, I replaced most of the buffer management code in
Sam with that from Acme, which was more efficient - it did the database
stuff in a different order that was one pass quicker. It's possible the old
code used an arena allocator, I don't remember, but it's possible you're
referring to the code in samterm, which grew up on the Blit and likely had
some compacting arena management code in it to keep the memory footprint
small. As always, though, my memory may be faulty; it compacts too often.

-rob


On Tue, Jun 29, 2021 at 8:20 AM silas poulson <silas8642@hotmail.co.uk>
wrote:

> Hi,
> 
> Recently discovered a blog post[1] stating Sam used to have arena
> based allocators.
> 
> Having difficulty finding more about this - does anyone know what the
> allocator looked like and why the source returned to using the
> standard allocators.
> 
> Silas
> 
> [1]https://jeremywsherman.com/2012/02/28/memory-allocation-in-sam/
> 

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Re: [9fans] Sam arena allocators

[silas poulson]

> On 28 Jun 2021, at 23:29, Rob Pike <robpike@gmail.com> wrote:
> After Acme was written, I replaced most of the buffer management code in Sam
> with that from Acme, which was more efficient 

Right, that makes sense.

> It's possible the old code used an arena allocator, I don't remember,
> but it's possible you're referring to the code in samterm, which grew up
> on the Blit and likely had some compacting arena management code in
> it to keep the memory footprint small.

Possibly, I’m still exploring the code.

Re-reading Sam paper though, memory management section seems to imply
custom allocator, ran on both terminal and host to efficiently hold strings in memory 
via variable length arrays.

> As always, though, my memory may be faulty; it compacts too often.

Ha

Silas
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Re: [9fans] Sam arena allocators

[noel.hunt]

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As Rob Pike pointed out, the compacting garbage collector was used in
severalof the programs written for the Blit. The source file in question
is 'gcalloc.c' and it seems to be in sam source as late as 10th Edition.
From a perusal of research source, it seems to have been used in jim, sam,
pads, mux amongst others.
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Re: [9fans] Sam arena allocators

[silas poulson]

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On 30 Jun 2021, at 00:44, noel.hunt@gmail.com<mailto:noel.hunt@gmail.com> wrote:
The source file in question is 'gcalloc.c' and it seems to be in sam
source as late as 10th Edition. From a perusal of research source, it
seems to have been used in jim, sam, pads, mux amongst others.

Right, thank you for that - forgot sources were available via list.

Will examine closely

Silas

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