Re: alsamm (was Re: [PD-dev] Re: [PD] RME hammerfall)

Hello,

Thanks, I think we should change this in code, I didnt do optimation on this, just a copy and paste from previous code.

The main point is, that data transfer in send_dacs is to memory mapped region of soundcardbuffer and therefore no other copy is needed, like I think done in jack, so it includes the copy (and add) loops burned by jack.

Anyway if we have a smarter recognition which channels have really corresponding dac/adc devices we could zero out the other channels once and dont need the copy loop for them which will improve a lot, since on mmap we are forced to use all channels or none.

mfg winfried

after some profiling, i figured out that the alsamm driver is burning a lot of cpu during the alsamm_send_dacs ... output of "opreport -l /usr/local/bin/pd"

CPU: CPU with timer interrupt, speed 0 MHz (estimated) Profiling through timer interrupt samples % symbol name 29630 38.6436 alsamm_send_dacs 5847 7.6257 tabosc4_tilde_perform 5578 7.2749 block_prolog 4451 5.8050 copyvec_simd 4362 5.6889 testaddvec_simd 3119 4.0678 oss_send_dacs 2019 2.6332 peakvec_simd 1577 2.0567 sighip_perform 1560 2.0346 dsp_tick 1410 1.8389 testcopyvec_simd 978 1.2755 sigthrow_perfsimd 973 1.2690 env_tilde_accum_simd 834 1.0877 zerovec_simd 780 1.0173 sys_getrealtime 698 0.9103 sys_domicrosleep 659 0.8595 plus_perf_simd

<snip>

there are two loops that slow down the thing:

5313 4.8734 : for (i = 0, fp2 = fp1 + chn*sys_dacblocksize; i < oframes; i++,fp2++)

           :          {

2296 2.1060 : float s1 = *fp2 * F32MAX;

           :            /* better but slower, better never clip ;-)
           :               buf[i]= CLIP32(s1); */

3278 3.0068 : buf[i]= ((int) s1 & 0xFFFFFF00); 1052 0.9650 : *fp2 = 0.0;

           :          }
           :      }

and

253 0.2321 : for (chn = 0; chn < ichannels; chn++) {

60  0.0550 :        t_alsa_sample32 *buf = (t_alsa_sample32 *)

dev->a_addr[chn];

17254 15.8265 : for (i = 0, fp2 = fp1 + chn*sys_dacblocksize; i < iframes; i++,fp2++)

           :          {
           :            /* mask the lowest bits, since subchannels info
           : can make zero samples nonzero */

10438 9.5744 : *fp2 = (float) ((t_alsa_sample32) (buf[i] & 0xFFFFFF00))

           :              * (1.0 / (float) INT32_MAX);
           :          }
           :      }

the problem is, that the samples have to be transfered from the sse registers

to the general purpose registers to do the bitmask operations: : 80ba444: movaps %xmm2,%xmm1

845 0.7751 : 80ba447: movss (%edx),%xmm0 1451 1.3309 : 80ba44b: mulss %xmm1,%xmm0 311 0.2853 : 80ba44f: cvttss2si %xmm0,%eax 1262 1.1576 : 80ba453: xor %al,%al 1705 1.5639 : 80ba455: mov %eax,(%esi,%ecx,4) 1052 0.9650 : 80ba458: movl $0x0,(%edx) 4581 4.2020 : 80ba45e: add $0x1,%ecx 2 0.0018 : 80ba461: mov 0xffffffe8(%ebp),%ebx 664 0.6091 : 80ba464: add $0x4,%edx

           : 80ba467:       cmp    %ebx,%ecx

 4  0.0037 : 80ba469:       jl     80ba447 <alsamm_send_dacs+0x12c>

and

           : 80ba68e:       movaps %xmm2,%xmm1

4652 4.2671 : 80ba691: mov (%esi,%ecx,4),%eax 12579 11.5382 : 80ba694: add $0x1,%ecx

           : 80ba697:       xor    %al,%al

70  0.0642 : 80ba699:       cvtsi2ss %eax,%xmm0

3665 3.3618 : 80ba69d: mulss %xmm1,%xmm0 2051 1.8813 : 80ba6a1: movss %xmm0,(%edx) 3737 3.4278 : 80ba6a5: add $0x4,%edx 888 0.8145 : 80ba6a8: mov 0xffffffe0(%ebp),%ebx 3 0.0028 : 80ba6ab: cmp %ebx,%ecx

           : 80ba6ad:       jl     80ba691 <alsamm_send_dacs+0x376>

i think the better way would be to hardcode these two loops with sse instructions, at least for x86 ... not sure, if this is also a problem on the ppc platform ...

cheers... tim