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

Marek Vasut
2015-11-25T12:16:12Z

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 ?

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 .