More on O_STREAMING (goodby read pauses)

From: J.A. Magallon (jamagallon@able.es)
Date: Wed Oct 09 2002 - 17:23:49 EST

Hi all...

I have discovered one other (good) side effect of O_STREAMING.

I tested it on my duap PII@400, ~900Mb RAM.

Timings:

Without O_STREAMING:
  0.00user 10.13system 0:41.16elapsed 24%CPU (0avgtext+0avgdata 0maxresident)k
  0inputs+0outputs (81major+2574minor)pagefaults 0swaps
With O_STREAMING:
  0.00user 11.03system 0:40.06elapsed 27%CPU (0avgtext+0avgdata 0maxresident)k
  0inputs+0outputs (81major+2574minor)pagefaults 0swaps

Memory:

Before
        total: used: free: shared: buffers: cached:
Mem: 926797824 228376576 698421248 0 20729856 95637504
Swap: 353644544 114688 353529856
MemTotal: 905076 kB
MemFree: 682052 kB
MemShared: 0 kB
Buffers: 20244 kB
Cached: 93284 kB
SwapCached: 112 kB
Active: 77284 kB
Inactive: 97160 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 905076 kB
LowFree: 682052 kB
SwapTotal: 345356 kB
SwapFree: 345244 kB
BigFree: 0 kB

After test without O_STREAMING:
        total: used: free: shared: buffers: cached:
Mem: 926797824 910376960 16420864 0 13369344 788623360
Swap: 353644544 1077248 352567296
MemTotal: 905076 kB
MemFree: 16036 kB
MemShared: 0 kB
Buffers: 13056 kB
Cached: 769088 kB
SwapCached: 1052 kB
Active: 83672 kB
Inactive: 759388 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 905076 kB
LowFree: 16036 kB
SwapTotal: 345356 kB
SwapFree: 344304 kB
BigFree: 0 kB

After test with O_STREAMING:
        total: used: free: shared: buffers: cached:
Mem: 926797824 228241408 698556416 0 20647936 95596544
Swap: 353644544 114688 353529856
MemTotal: 905076 kB
MemFree: 682184 kB
MemShared: 0 kB
Buffers: 20164 kB
Cached: 93244 kB
SwapCached: 112 kB
Active: 77200 kB
Inactive: 97112 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 905076 kB
LowFree: 682184 kB
SwapTotal: 345356 kB
SwapFree: 345244 kB
BigFree: 0 kB

But I did the test with an addition: read a 1Gb file and print an '*'
after every 10M. Without O_STREAMING, when memory fills, the 'progress
bar' stalls for a few seconds while pages are sent to disk.
So the patch also favours a constant sustained rate of read from the
disk. Very interesting for things like video edition and so on.
I like it ;).

Thanks. 

-- 
J.A. Magallon <jamagallon@able.es>      \                 Software is like sex:
werewolf.able.es                         \           It's better when it's free
Mandrake Linux release 9.1 (Cooker) for i586
Linux 2.4.20-pre10-jam1 (gcc 3.2 (Mandrake Linux 9.0 3.2-2mdk))
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This archive was generated by hypermail 2b29 : Tue Oct 15 2002 - 22:00:33 EST