[Tarantool-patches] [PATCH v2] refactoring: drop excess 16Kb bss buffer

[Leonid Vasiliev]

Hi.

On 1/29/20 4:36 PM, Sergey Ostanevich wrote:
> Hi!
> 
> Thanks for the patch!
> 
> LGTM after updates below.
> 
> Regards,
> Sergos
> 
> 
> On 23 Jan 23:04, Vladislav Shpilevoy wrote:
>> Hi! Thanks for the patch!
>>
>> I agree with everything what Leonid said.
> 
> I will object both assertion and NULL handling. Just have a look:
> 
>>> +   char *backtrace_buf = (char *)static_alloc(SMALL_STATIC_SIZE);
> 
> And in static_reserve(size_t size) called from static_alloc():
> 
>                  if (size > SMALL_STATIC_SIZE)
>                                          return NULL;
> 
> is the only place NULL can be returned. No need to test if
> SMALL_STATIC_SIZE > SMALL_STATIC_SIZE, just ask me :)

Hmm, it's sounds like:"Client must known about implementation of library 
function". But implementation can be changed with the contract save.

> 
> 
> 
>>
>> On 23/01/2020 09:44, Sergey Kaplun wrote:
>>> We already have 12Kb thread-safe static buffer
>>> in `lib/small/small/static.h`, that can be used instead of 16Kb
>>> bss buffer in `src/lib/core/backtrace.cc` for backtrace payload.
>>> Closes #4650
>>> ---
>>>
>>> branch: https://github.com/tarantool/tarantool/tree/skaplun/drop-bss-buff
>>> issue: https://github.com/tarantool/tarantool/issues/4650
>>>
>>>   src/lib/core/backtrace.cc | 8 +++++---
>>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/src/lib/core/backtrace.cc b/src/lib/core/backtrace.cc
>>> index 77f77b05c..c70576b53 100644
>>> --- a/src/lib/core/backtrace.cc
>>> +++ b/src/lib/core/backtrace.cc
>>> @@ -33,6 +33,7 @@
>>>   
>>>   #include <stdlib.h>
>>>   #include <stdio.h>
>>> +#include <assert.h>
>>>   
>>>   #include <cxxabi.h>
>>>   
>>> @@ -47,6 +48,7 @@
>>>   #include <libunwind.h>
>>>   
>>>   #include "small/region.h"
>>> +#include "small/static.h"
>>>   /*
>>>    * We use a global static buffer because it is too late to do any
>>>    * allocation when we are printing backtrace and fiber stack is
> 
> Just change "global static buffer" for the "static buffer interface".
> 
>>> @@ -55,8 +57,6 @@
>>>   
>>>   #define BACKTRACE_NAME_MAX 200
>>>   
>>> -static char backtrace_buf[4096 * 4];
>>> -
>>>   static __thread struct region cache_region;
>>>   static __thread struct mh_i64ptr_t *proc_cache = NULL;
>>>   
>>> @@ -140,8 +140,10 @@ backtrace()
>>>   	unw_getcontext(&unw_context);
>>>   	unw_cursor_t unw_cur;
>>>   	unw_init_local(&unw_cur, &unw_context);
>>> +	char *backtrace_buf = (char *)static_alloc(SMALL_STATIC_SIZE);
>>> +	assert(backtrace_buf);
>>>   	char *p = backtrace_buf;
>>> -	char *end = p + sizeof(backtrace_buf) - 1;
>>> +	char *end = p + SMALL_STATIC_SIZE - 1;
>>>   	int unw_status;
>>>   	*p = '\0';
>>>   	while ((unw_status = unw_step(&unw_cur)) > 0) {
>>>