Messages in this thread | ![/](/images/icornerl.gif) | | Subject | RE: problem with 2.6.13.[0-2] | From | David Ronis <> | Date | Wed, 28 Sep 2005 21:37:10 -0400 |
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On Tue, 2005-09-27 at 22:55 -0400, Parag Warudkar wrote: > > > DMA is on in both 2.6.12.6 and in 2.6.13.2. Here's what hdparm > > /dev/hda gives: > > > > in 2.6.12.6: > > > > /dev/hda: > > multcount = 16 (on) > > IO_support = 0 (default 16-bit) > > unmaskirq = 0 (off) > > using_dma = 1 (on) > > keepsettings = 0 (off) > > readonly = 0 (off) > > readahead = 256 (on) > > geometry = 65535/16/63, sectors = 195371568, start = 0 > > > > in 2.6.13.2 it's the same, except for > > > > multcount = 0 (off) > > > > Could this be the problem, and if so, would setting multcount to on > > fix it? (I take it hdparm -m 16 /dev/hda would do it) > > I doubt if multcount will make a difference, but you can try. > Probably next best thing to do is profile the slow kernel to find where it > is spending time. (pass profile=2 on kernel command line and use > readprofile or use oprofile). > > Did you try hdparm -tT /dev/hda? It's going to be slow, thats for sure > from what you described but try that and then post dmesg (for both > kernels) and profile results - may be someone will get a clue from that. > > Parag > >
Hi Parag,
Here's what I get:
In 2.6.12.6:
/dev/hda: Timing cached reads: 1140 MB in 2.00 seconds = 569.80 MB/sec Timing buffered disk reads: 102 MB in 3.02 seconds = 33.80 MB/sec
In 2.6.13.2:
/dev/hda: Timing cached reads: 28 MB in 2.15 seconds = 13.03 MB/sec Timing buffered disk reads: 14 MB in 3.30 seconds = 4.24 MB/sec
and after hdparm -m 16 /dev/hda (recall this is the default in 2.6.12.6)
/dev/hda: Timing cached reads: 24 MB in 2.05 seconds = 11.73 MB/sec Timing buffered disk reads: 36 MB in 3.11 seconds = 11.56 MB/sec
I ran thing a few times in each case and the results were close. There was nothing in dmesg.
David
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