On Sun, Feb 01, 2015 at 03:38:42AM +0100, Albert ARIBAUD wrote: > Hello Przemyslaw, > > On Wed, 28 Jan 2015 13:55:42 +0100, Przemyslaw Marczak > <p.marc...@samsung.com> wrote: > > For ARM architecture, enable the CONFIG_USE_ARCH_MEMSET/MEMCPY, > > will highly increase the memset/memcpy performance. This is able > > thanks to the ARM multiple register instructions. > > > > Unfortunatelly the relocation is done without the cache enabled, > > so it takes some time, but zeroing the BSS memory takes much more > > longer, especially for the configs with big static buffers. > > > > A quick test confirms, that the boot time improvement after using > > the arch memcpy for relocation has no significant meaning. > > The same test confirms that enable the memset for zeroing BSS, > > reduces the boot time. > > > > So this patch enables the arch memset for zeroing the BSS after > > the relocation process. For ARM boards, this can be enabled > > in board configs by defining: 'CONFIG_USE_ARCH_MEMSET'. > > Since the issue is that zeroing is done one word at a time, could we > not simply clear r3 as well as r2 (possibly even r4 and r5 too) and do > a double (possibly quadruple) write loop? That would avoid calling a > libc routine from the almost sole file in U-Boot where a C environment > is not necessarily granted.
So this brings up something I've wondered about for a long while. We
have arch/arm/lib/mem{set,cpy}.S which are old copies from the linux
kernel. The kernel uses them for all ARM platforms. Why do we not
always use these functions? I have a very vague notion it was a size
thing...
--
Tom
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