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

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

[Sergey Kaplun]

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
@@ -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) {
-- 
2.24.1

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

[Leonid Vasiliev]

On 1/23/20 11:44 AM, 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

May be to change the comment or relocate it?

> @@ -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);

Do a check on NULL for Release?

>   	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) {
> 

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

[Vladislav Shpilevoy]

Hi! Thanks for the patch!

I agree with everything what Leonid said.

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
> @@ -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) {
> 

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

[Sergey Ostanevich]

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 :)



> 
> 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) {
> > 

Re: [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) {
>>>

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

[Sergey Kaplun]

Hi!

Thanks for your feedback!

On 30.01.20, Leonid Vasiliev wrote:
> 
> 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.
> 

To be honest, I do not see any dependencies on internal API in this,
since the module determines SMALL_STATIC_SIZE and provides

    extern __thread char static_storage_buffer[SMALL_STATIC_SIZE];

- all of this is part of API, isn't it?

Proposal: we can use sizeof(static_storage_buffer) to avoid usage
of "magic" SMALL_STATIC_SIZE.

> > 
> > 
> > 
> >>
> >> 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) {
> >>>

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

[Leonid Vasiliev]

On 2/1/20 1:30 AM, Sergey Kaplun wrote:
> Hi!
> 
> Thanks for your feedback!
> 
> On 30.01.20, Leonid Vasiliev wrote:
>>
>> 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.
>>
> 
> To be honest, I do not see any dependencies on internal API in this,
> since the module determines SMALL_STATIC_SIZE and provides
> 
>      extern __thread char static_storage_buffer[SMALL_STATIC_SIZE];
> 
> - all of this is part of API, isn't it?
> 
> Proposal: we can use sizeof(static_storage_buffer) to avoid usage
> of "magic" SMALL_STATIC_SIZE.
> 

Ok)
Just for clarity.
My point of view on an interface of small static_alloc function: "It's 
return a pointer which can be a NULL and I must to check it". In my mind 
the realization of the static_alloc can be changed to "return NULL;" and 
my code must continue to work fine.
Your point of  view: "static_alloc can alloc/reserve of size <= 
SMALL_STATIC_SIZE in any case and it's interface guarantees this".
In this case I'm agree with Sergey Ostanevich.

>>>
>>>
>>>
>>>>
>>>> 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) {
>>>>>