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SubjectRe: 2.4 disk speed 66% slowdown...
I think we're on to something.  I did gen's of the kernel with
the following configs: 1) 2.2.17 (w/apm), 2) 2.4(w/apm), 3) 2.4(w/o apm).
The apm seems to be a red herring in terms of actual performance
hit. It seems to count apm time as 'system' time instead of 'idle'.

Kernel gen times were:
1) real 6m33.046s, user 6m1.380s, sys 0m18.450s
2) 6m45s real 6m12s user 0m26s sys
3) real 6m49.275s, user 6m14.740s, sys 0m26.690s

The REAL problem was in disk performance. The apm made no difference:

hdparm -t /dev/hda1 /dev/hda3 /dev/hda4 /dev/hda5 /dev/hda7
1) 2.2.17
/dev/hda1: Timing buffered disk reads: 64 MB in 4.76 seconds = 13.45 MB/sec
/dev/hda3: Timing buffered disk reads: 64 MB in 4.57 seconds = 14.00 MB/sec
/dev/hda4: Timing buffered disk reads: 64 MB in 6.47 seconds = 9.89 MB/sec
/dev/hda5: Timing buffered disk reads: 64 MB in 5.08 seconds = 12.60 MB/sec
/dev/hda7: Timing buffered disk reads: 64 MB in 5.10 seconds = 12.55 MB/sec

2) 2.4 w/apm
/dev/hda1: Timing buffered disk reads: 64 MB in 16.03 seconds = 3.99 MB/sec
/dev/hda3: Timing buffered disk reads: 64 MB in 15.87 seconds = 4.03 MB/sec
/dev/hda4: Timing buffered disk reads: 64 MB in 15.67 seconds = 4.08 MB/sec
/dev/hda5: Timing buffered disk reads: 64 MB in 15.82 seconds = 4.05 MB/sec
/dev/hda7: Timing buffered disk reads: 64 MB in 15.85 seconds = 4.04 MB/sec

3) 2.4 w/o apm
/dev/hda1: Timing buffered disk reads: 64 MB in 16.02 seconds = 4.00 MB/sec
/dev/hda3: Timing buffered disk reads: 64 MB in 15.88 seconds = 4.03 MB/sec
/dev/hda4: Timing buffered disk reads: 64 MB in 15.67 seconds = 4.08 MB/sec
/dev/hda5: Timing buffered disk reads: 64 MB in 15.85 seconds = 4.04 MB/sec
/dev/hda7: Timing buffered disk reads: 64 MB in 15.86 seconds = 4.04 MB/sec

Mine is on a ide1 device on a Dell Insp. 7500:
hdparm -i /dev/hda (from 2.2.17)

/dev/hda:

Model=IBM-DARA-225000, FwRev=SHAOA54A, SerialNo=SQASQ202564
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
BuffType=3(DualPortCache), BuffSize=418kB, MaxMultSect=16, MultSect=off
DblWordIO=no, OldPIO=2, DMA=yes, OldDMA=2
CurCHS=17475/15/63, CurSects=16513875, LBA=yes, LBAsects=49577472
tDMA={min:120,rec:120}, DMA modes: mword0 mword1 mword2
IORDY=on/off, tPIO={min:240,w/IORDY:120}, PIO modes: mode3 mode4
UDMA modes: mode0 mode1 *mode2 mode3 mode4
Drive Supports : ATA/ATAPI-4 T13 1153D revision 17 : ATA-1 ATA-2 ATA-3 ATA-4


"Barry K. Nathan" wrote:
> Specifically, the following command read off the disk more slowly:
>
> gzip -1 < /dev/hda | nc some_other_box some_port -w 1
...
--
Linda A Walsh | Trust Technology, Core Linux, SGI
law@sgi.com | Voice: (650) 933-5338
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