[Tarantool-patches] [PATCH v2] refactoring: drop excess 16Kb bss buffer
Sergey Kaplun
skaplun at tarantool.org
Sat Feb 1 01:30:14 MSK 2020
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) {
> >>>
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