[U-Boot] [PATCH] arm: mx6: Reduce SPL malloc pool size

Marek Vasut
2015-11-25T13:32:24Z

On Wednesday, November 25, 2015 at 02:15:13 PM, Przemyslaw Marczak wrote:
> On 11/25/2015 01:16 PM, Marek Vasut wrote:
> > On Wednesday, November 25, 2015 at 01:00:41 PM, Przemyslaw Marczak wrote:
> >> Hello Marek,
> >>
> >> On 11/25/2015 11:56 AM, Marek Vasut wrote:
> >>> On Wednesday, November 25, 2015 at 11:40:36 AM, Przemyslaw Marczak wrote:
> >>>> Hello Tim, Marek
> >>>>
> >>>> On 11/20/2015 10:40 PM, Tim Harvey wrote:
> >>>>> On Fri, Nov 20, 2015 at 12:43 PM, Marek Vasut <marex@denx.de> wrote:
> >>>>>> Using 50 MiB malloc pool in SPL is nonsense. Since the caches are
> >>>>>> not enabled in SPL, it takes 2 seconds to init the pool and has no
> >>>>>> obvious benefit. Reduce the size to 1 MiB.
> >>>>>>
> >>>>>> Signed-off-by: Marek Vasut <marex@denx.de>
> >>>>>> Cc: Stefano Babic <sbabic@denx.de>
> >>>>>> Cc: Tim Harvey <tharvey@gateworks.com>
> >>>>>> ---
> >>>>>>
> >>>>>> include/configs/imx6_spl.h | 6 +++---
> >>>>>> 1 file changed, 3 insertions(+), 3 deletions(-)
> >>>>>>
> >>>>>> diff --git a/include/configs/imx6_spl.h b/include/configs/imx6_spl.h
> >>>>>> index 1744f2c..43ce7fe 100644
> >>>>>> --- a/include/configs/imx6_spl.h
> >>>>>> +++ b/include/configs/imx6_spl.h
> >>>>>> @@ -63,15 +63,15 @@
> >>>>>>
> >>>>>> #if defined(CONFIG_MX6SX) || defined(CONFIG_MX6UL) ||
> >>>>>> defined(CONFIG_MX6SL) #define CONFIG_SPL_BSS_START_ADDR
> >>>>>> 0x88200000
> >>>>>>
> >>>>>> -#define CONFIG_SPL_BSS_MAX_SIZE 0x100000 /* 1 MB */
> >>>>>> +#define CONFIG_SPL_BSS_MAX_SIZE 0x100000 /* 1
> >>>>>> MB */
> >>>>>>
> >>>>>> #define CONFIG_SYS_SPL_MALLOC_START 0x88300000
> >>>>>>
> >>>>>> -#define CONFIG_SYS_SPL_MALLOC_SIZE 0x3200000 /* 50 MB */
> >>>>>> +#define CONFIG_SYS_SPL_MALLOC_SIZE 0x100000 /* 1
> >>>>>> MB */
> >>>>>>
> >>>>>> #define CONFIG_SYS_TEXT_BASE 0x87800000
> >>>>>> #else
> >>>>>> #define CONFIG_SPL_BSS_START_ADDR 0x18200000
> >>>>>> #define CONFIG_SPL_BSS_MAX_SIZE 0x100000
> >>>>>> /* 1 MB */ #define CONFIG_SYS_SPL_MALLOC_START 0x18300000
> >>>>>>
> >>>>>> -#define CONFIG_SYS_SPL_MALLOC_SIZE 0x3200000 /* 50 MB */
> >>>>>> +#define CONFIG_SYS_SPL_MALLOC_SIZE 0x100000 /* 1 MB */
> >>>>>>
> >>>>>> #define CONFIG_SYS_TEXT_BASE 0x17800000
> >>>>>> #endif
> >>>>>> #endif
> >>>>>>
> >>>>>> --
> >>>>>> 2.1.4
> >>>>>
> >>>>> Acked-by: Tim Harvey <tharvey@gateworks.com>
> >>>>>
> >>>>> thanks for dropping 2 secs off our time to boot!
> >>>>>
> >>>>> Tim
> >>>>
> >>>> The boot time for SPL and U-Boot can be reduced more if
> >>>> CONFIG_SYS_MALLOC_CLEAR_ON_INIT is unset (default is set).
> >>>
> >>> This might confuse DM, so I don't want this. DM checks if it's
> >>> structures were already inited and if we don't clear the malloc area,
> >>> they would be.
> >>
> >> DM is safe - it uses calloc() for it's structures and also driver's
> >> static structures are zeroed. Only some private data which is not
> >> allocated by DM can be risky to use.
> >>
> >> To be precise - we don't use malloc() to get pointer for zeroed memory,
> >> this is the job for the calloc().
> >>
> >> So any code with bad use of malloc() should be fixed ASAP.
> >>
> >> If you assume that clear the malloc pool at boot is safe to use, then
> >> I'm asking you, what about the sequence malloc/free/malloc for
> >> potentially the same area? You can't be sure that the second returned
> >> pointer after calling free() - points to the initially zeroed pool.
> >>
> >> We don't clean the malloc pool for configs that we maintain and we
> >> didn't noticed any issues related to this. And the boot time is reduced
> >> significantly.
> >
> > Do you use DM in SPL ?
>
> No, we don't use the SPL - for the boards which we maintain.

OK

> > I just checked and I see it's probably only the GD which needs to be
> > cleared out, so we should indeed be safe. In which case, patch is
> > welcome to enable CONFIG_SYS_MALLOC_CLEAR_ON_INIT .
>
> Yes I can see also for the Exynos SPL, that GD is manually cleared.
>
> But disabling the default CONFIG_SYS_MALLOC_CLEAR_ON_INIT, will help you
> in reducing the U-Boot init time.
> Just try and if you can easy measure the real difference for
> enable/disable this config - share the results - it can give us an
> interesting conclusions.

Sure, thanks for the hint, but I still don't see any reason for having 50 MiB
malloc area in SPL ;-)