Re: [ST-devel] [ST-users] problem of stack size in st_thread_create()

[Alfred Z. <alf...@gm...>]

Oh my god!

+ _ST_PAGE_SIZE - 1

if stk_size is just x times of the _ST_PAGE_SIZE, the integer division will
return exactly x b/c of the -1.

if stk_size is smaller than x times of _ST_PAGE_SIZE, the integer division
will return exactly x, and ignore the remaining >x but <x+1

That is smart!
If the purpose is in the comment or docs will be better to understand

Thanks a lot, John!

Alfred

On Wed, Aug 10, 2011 at 1:11 PM, John Newton <jn...@gm...> wrote:

> The line you are asking about is a "round up" to the next page size
> calculation.
>
> For example, if getpagesize() returns 4096, and the "stk_size" parameter is
> 10,000 it would round up to the next even page size. (the division is doing
> integer math)
>
> Hope this helps!
>
> On Wed, Aug 10, 2011 at 9:06 AM, Alfred Zhong <alf...@gm...>wrote:
>
>> Hi,
>> I am new to state thread library and am reading the source code of ST to
>> study implementation of threading.
>>
>> in the st_thread_create() function
>>
>> there is this code piece
>>
>> if (stk_size == 0)
>>     stk_size = ST_DEFAULT_STACK_SIZE;  // I know this is to set the stack
>> size to a default size, if the input size is 0
>>   stk_size = ((stk_size + _ST_PAGE_SIZE - 1) / _ST_PAGE_SIZE) *
>> _ST_PAGE_SIZE; //what does this mean?
>>
>> Look like it equals (stk_size + ST_PAGE_SIZE -1) unless the previous
>> division gives 0.
>>
>> I am totally confused and can't find the answer in the code or the docs,
>> please help!
>>
>> Thanks a lot!
>> Alfred
>>
>>
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