DOS ain't dead - NTVDM speed (or lack thereof)

NTVDM speed (or lack thereof) (Announce)

posted by Ninho , 15.02.2011, 12:26
(edited by Ninho on 15.02.2011, 12:43)

>> I killed off all Dos use on normal windows systems in 2002-2003 when I
>> moved to Win2000. (Since dos fullscreen apps are much slower on NT than
>> win32 stuff)

> Except for LZMA-FPC, I've never seen any significant slowdown with 32-bit
> DOS apps. So nyah.

I would not have mentioned the following in a DOS forum, but you kinda started me... For CPU bound apps, NTVDM indeed is awfully slow - independent of display mode.

A craftfuly enough optimised program of mine doing heavy and lengthy calculations during hours, entirely in registers (avoiding memory accesses, even from the data caches!), runs about 4 times slower -wall time- in Windows 2k than in pure DOS ! And this is in concurrence with NO other (user) tasks ! And running maximised in foreground (just in case, but no joice).

The cause is, of course, you cannot stop Windows multitasking°, and it consumes 3 times more time doing whatever obscure and (in this case) evidently useless bookkeeping just in order to stay alive!!!
(edit) sorry I forgot to stress, another cause to this extreme slowdown is that every context switch disrupts caches thus ruining the optimisation I mentionned (edit ends)

° Or can you ? I did some research, even asked the Sysinternals gurus, never found any way to "tame" the beast, albeit means to increase the time quantum alloted to the task of interest. Oddly, it's possible to decrease the quantum (for "multimedia" purposes. burp!)

Under the virtual DOS box of Windows 9x, the slowdown if much less than NT, but still significant (unbearable for the lengthy calculations). Except of course unlike NT you /could/ CLI under 9x ;=)

One more reason to keep our DOS living !

---
Ninho

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Complete thread:

PCI phased out? - marcov, 09.02.2011, 12:51 (Announce)
- PCI phased out? - RayeR, 09.02.2011, 16:24
  - PCI phased out? - marcov, 10.02.2011, 16:02
    - PCI phased out? - RayeR, 10.02.2011, 17:57
      - PCI phased out? - marcov, 10.02.2011, 21:10
        PCI phased out? - RayeR, 11.02.2011, 00:25
        PCI phased out? - marcov, 11.02.2011, 10:56
        PCI phased out? - RayeR, 12.02.2011, 02:34
        PCI phased out? - marcov, 12.02.2011, 12:45
        PCI phased out? - Rugxulo, 12.02.2011, 21:28
        PCI phased out? - DOS386, 13.02.2011, 06:02
        PCI phased out? - RayeR, 13.02.2011, 16:11
        PCI phased out? - DOS386, 14.02.2011, 09:27
        PCI phased out? - marcov, 14.02.2011, 10:29
        NTVDM speed (or lack thereof) - Ninho, 15.02.2011, 12:26
        NTVDM speed (or lack thereof) - Rugxulo, 15.02.2011, 14:26
        NTVDM speed (or lack thereof) - marcov, 15.02.2011, 14:33
        NTVDM speed (or lack thereof) - Ninho, 15.02.2011, 20:27
        NTVDM speed (or lack thereof) - Rugxulo, 15.02.2011, 23:21
        NTVDM speed (or lack thereof) - marcov, 16.02.2011, 09:24
        NTVDM speed (or lack thereof) - Ninho, 16.02.2011, 20:04
        NTVDM speed (or lack thereof) - RayeR, 16.02.2011, 01:50
        NTVDM speed (or lack thereof) - Rugxulo, 16.02.2011, 02:24
        NTVDM speed (or lack thereof) - RayeR, 16.02.2011, 10:41
        NTVDM speed (or lack thereof) - rr, 17.02.2011, 20:33
        PCI phased out? - RayeR, 14.02.2011, 15:45
        PCI phased out? - marcov, 15.02.2011, 13:40
        PCI phased out? - RayeR, 15.02.2011, 15:15
        PCI phased out? - marcov, 15.02.2011, 18:43
        PCI phased out? - RayeR, 15.02.2011, 19:46
        PCI phased out? - marcov, 16.02.2011, 10:36
        PCI phased out? - RayeR, 16.02.2011, 12:22
        PCI phased out? - marcov, 16.02.2011, 15:38
        PCI phased out? - Rugxulo, 16.02.2011, 19:18
        PCI phased out? - marcov, 16.02.2011, 21:22
        PCI phased out? - Rugxulo, 17.02.2011, 02:28
        EOD (was "PCI phased out?") - DOS386, 17.02.2011, 06:44
        PCI phased out? - marcov, 17.02.2011, 19:44
        PCI phased out? - Rugxulo, 18.02.2011, 08:39
        PCI phased out? - marcov, 18.02.2011, 09:30
        PCI phased out? - Rugxulo, 21.02.2011, 07:43
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        PCI phased out? - Rugxulo, 11.03.2011, 00:06
        PCI phased out? - roytam, 11.03.2011, 07:52
        PCI phased out? - Rugxulo, 17.03.2011, 04:16
        PCI phased out? - Ninho, 19.02.2011, 10:56
        PCI phased out? - Rugxulo, 21.02.2011, 07:15
        PCI phased out? - marcov, 21.02.2011, 14:09
        PCI phased out? - Laaca, 21.02.2011, 14:22
        PCI phased out? - marcov, 21.02.2011, 14:47
        PCI phased out? - roytam, 22.02.2011, 04:26
        PCI phased out? - RayeR, 22.02.2011, 13:29
        PCI phased out? - RayeR, 22.02.2011, 23:44
        PCI phased out? - Ninho, 23.02.2011, 17:39
        PCI phased out? - RayeR, 23.02.2011, 19:47
        PCI phased out? - Ninho, 23.02.2011, 19:56
        PCI phased out? - RayeR, 23.02.2011, 23:27
        PCI phased out? - RayeR, 24.02.2011, 14:37
        PCI phased out? - Rugxulo, 16.03.2011, 04:58
        PCI phased out? - RayeR, 18.02.2011, 14:28
        PCI phased out? - marcov, 18.02.2011, 14:56
        PCI phased out? - roytam, 29.01.2015, 03:45