IDE DMA disabled with via82cxxx on kernels >= 2.5.35
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Recent 2.5 kernels boot with "DMA disabled".
It turns it on again but forgets to tell you. Its on the fix list but for 2.4 first
Actual throughput on Athlon is better then hdparm lets on. A dd test on 2.5.53-mm1 shows about 120 MB/sec for a file that fits in memory.
# time dd if=/dev/zero of=/tmp/junk bs=4M count=100 100+0 records in 100+0 records out
real 0m3.312s user 0m0.002s sys 0m3.267s
# ls -lh /tmp/junk -rw-r--r-- 1 root root 400M Jan 13 21:43 /tmp/junk
hdparm -tT on the K6/2 shows similar throughput between 2.4 and 2.5.
Maybe my hdparm is just wacky on 2.5.
2.4.20-pre3-jam1:
/dev/hda:
Timing buffer-cache reads: 128 MB in 0.70 seconds =182.86 MB/sec
Timing buffered disk reads: 64 MB in 2.07 seconds = 30.92 MB/sec
2.5.53-mm1
/dev/hda:
Timing buffer-cache reads: 128 MB in 7.20 seconds = 17.78 MB/sec
Timing buffered disk reads: 64 MB in 19.66 seconds = 3.26 MB/sec
Signature · 2 lines
Randy Hron http://home.earthlink.net/~rwhron/kernel/bigbox.html
Quoted 7 lines · On Mon January 13 2003 18:49, [email protected] wrote:
2.4.20-pre3-jam1:
/dev/hda:
Timing buffer-cache reads: 128 MB in 0.70 seconds =182.86 MB/sec
Timing buffered disk reads: 64 MB in 2.07 seconds = 30.92 MB/sec
Quoted 5 lines
2.5.53-mm1
/dev/hda:
Timing buffer-cache reads: 128 MB in 7.20 seconds = 17.78 MB/sec
Timing buffered disk reads: 64 MB in 19.66 seconds = 3.26 MB/sec
2.5.53-mm1 had a dud patch in it which made part of the kernel think HZ=100, other parts think HZ=1000, depending on whether the .c file happened to include config.h before including param.h.
Hence your nice 10x discrepancy.