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From: Michal Simek on 13 Apr 2010 04:10
Steven J. Magnani wrote:
> memcpy performance was measured on a noMMU system having a barrel shifter,
> 4K caches, and 32-byte write-through cachelines. In this environment,
> copying word-aligned data in word-sized chunks appears to be about 3% more
> efficient on packet-sized buffers (1460 bytes) than copying in cacheline-sized
> chunks.
>
> Skip to word-based copying when buffers are both word-aligned.
>
> Signed-off-by: Steven J. Magnani <steve(a)digidescorp.com>

I added this patch to next branch and I will keep it there for now.

1. I agree that we need several patches like this.
2. The improvement could be there and likely it is but 3% improvement
could be caused for different reason.
3. There is necessary to measure it on several hw design and cache
configurations to be sure that your expectation is correct.
4. The best will be to monitoring cache behavior but currently there is
no any tool which could easily help us with it.

I will talk to xilinx how to monitoring it.

Thanks,
Michal


> ---
> diff -uprN a/arch/microblaze/lib/fastcopy.S b/arch/microblaze/lib/fastcopy.S
> --- a/arch/microblaze/lib/fastcopy.S 2010-04-09 21:52:36.000000000 -0500
> +++ b/arch/microblaze/lib/fastcopy.S 2010-04-12 15:37:44.000000000 -0500
> @@ -69,37 +69,13 @@ a_dalign_done:
> blti r4, a_block_done
>
> a_block_xfer:
> - andi r4, r7, 0xffffffe0 /* n = c & ~31 */
> - rsub r7, r4, r7 /* c = c - n */
> -
> andi r9, r6, 3 /* t1 = s & 3 */
> - /* if temp != 0, unaligned transfers needed */
> - bnei r9, a_block_unaligned
> -
> -a_block_aligned:
> - lwi r9, r6, 0 /* t1 = *(s + 0) */
> - lwi r10, r6, 4 /* t2 = *(s + 4) */
> - lwi r11, r6, 8 /* t3 = *(s + 8) */
> - lwi r12, r6, 12 /* t4 = *(s + 12) */
> - swi r9, r5, 0 /* *(d + 0) = t1 */
> - swi r10, r5, 4 /* *(d + 4) = t2 */
> - swi r11, r5, 8 /* *(d + 8) = t3 */
> - swi r12, r5, 12 /* *(d + 12) = t4 */
> - lwi r9, r6, 16 /* t1 = *(s + 16) */
> - lwi r10, r6, 20 /* t2 = *(s + 20) */
> - lwi r11, r6, 24 /* t3 = *(s + 24) */
> - lwi r12, r6, 28 /* t4 = *(s + 28) */
> - swi r9, r5, 16 /* *(d + 16) = t1 */
> - swi r10, r5, 20 /* *(d + 20) = t2 */
> - swi r11, r5, 24 /* *(d + 24) = t3 */
> - swi r12, r5, 28 /* *(d + 28) = t4 */
> - addi r6, r6, 32 /* s = s + 32 */
> - addi r4, r4, -32 /* n = n - 32 */
> - bneid r4, a_block_aligned /* while (n) loop */
> - addi r5, r5, 32 /* d = d + 32 (IN DELAY SLOT) */
> - bri a_block_done
> + /* if temp == 0, everything is word-aligned */
> + beqi r9, a_word_xfer
>
> a_block_unaligned:
> + andi r4, r7, 0xffffffe0 /* n = c & ~31 */
> + rsub r7, r4, r7 /* c = c - n */
> andi r8, r6, 0xfffffffc /* as = s & ~3 */
> add r6, r6, r4 /* s = s + n */
> lwi r11, r8, 0 /* h = *(as + 0) */
>


--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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