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 Fri, 24 Jan 2020 01:04:58 +0300 (MSK)
References: <20200123084445.7452-1-skaplun@tarantool.org>
From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Message-ID: <290fd1a1-022d-d0cf-d823-df6008872029@tarantool.org>
Date: Thu, 23 Jan 2020 23:04:56 +0100
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Subject: Re: [Tarantool-patches] [PATCH v2] refactoring: drop excess 16Kb
 bss buffer
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To: Sergey Kaplun <skaplun@tarantool.org>, tarantool-patches@dev.tarantool.org

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) {
>