Messages in this thread | | | Date | Sat, 15 Jul 2000 18:26:09 +0200 | From | Roger Larsson <> | Subject | Re: [DATAPOINT2] latencies for test4 - new info |
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Hi again,
Made a mistake in this report. I was actually running against the older WDC AC22100H. But I have now retested with the newer WDC AC33200L and the result is the same. I get worse latencies with the AC33200L (latencies from audio interrupt with a SCHED_FIFO process that itself does no disk IO)
The pattern looks like the new WD disk has fewer but longer spikes than the Seagate.
[Note: there are probably lots of even better disks than the Seagate - bought it since it is big and cheap (quiet too)]
/RogerL
Roger Larsson wrote: > > Hi, > > I made a HW patch. > Added a Seagate U10 ST320423A (20,4 GB) > > <6>Uniform Multi-Platform E-IDE driver Revision: 6.31 > <4>ide: Assuming 30MHz system bus speed for PIO modes > <4>PIIX3: IDE controller on PCI bus 00 dev 39 > <4>PIIX3: chipset revision 0 > <4>PIIX3: not 100% native mode: will probe irqs later > <4> ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:pio, hdb:pio > <4> ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc:pio, hdd:pio > <4>hda: WDC AC33200L, ATA DISK drive > <4>hdb: ST320423A, ATA DISK drive > <4>hdc: WDC AC22100H, ATA DISK drive > <4>ide0 at 0x1f0-0x1f7,0x3f6 on irq 14 > <4>ide1 at 0x170-0x177,0x376 on irq 15 > <6>hda: 6346368 sectors (3249 MB) w/256KiB Cache, CHS=787/128/63, (U)DMA > <6>hdb: 40011300 sectors (20486 MB) w/512KiB Cache, CHS=2490/255/63, > (U)DMA > <6>hdc: 4124736 sectors (2112 MB) w/128KiB Cache, CHS=4092/16/63, DMA > > And did my streaming test against it instead of the WDCAC33200L. > > Performance doubled as it should, sustained throuput should be a lot > better for the new Seagate. > > But more interesting is that latencies went way down - why ? > (running with Andrews low latency patch) > > # first run only DMA, readahead 8 > > Jul 15 01:19:51 dox kernel: Latency 5ms PID 2 % kswapd > Jul 15 01:26:24 dox kernel: Latency 7ms PID 0 % swapper > > # second run, multicount 8, 32bit, unmaskirq, DMA, readahead 8 > > Jul 15 01:33:47 dox kernel: Latency 8ms PID 2 % kswapd > Jul 15 01:33:47 dox kernel: Trace: [shrink_mmap+66/532] > Jul 15 01:34:04 dox kernel: Latency 5ms PID 328 % bash > Jul 15 01:34:04 dox kernel: Trace: [__mark_buffer_dirty+54/56] > Jul 15 01:34:09 dox kernel: Latency 11ms PID 2 % kswapd > Jul 15 01:34:09 dox kernel: Trace: [shrink_mmap+66/532] > Jul 15 01:34:36 dox kernel: Latency 6ms PID 2 % kswapd > Jul 15 01:34:37 dox kernel: Trace: [shrink_mmap+66/532] > Jul 15 01:35:54 dox kernel: Latency 5ms PID 2 % kswapd > Jul 15 01:35:55 dox kernel: Trace: [shrink_mmap+66/532] > Jul 15 01:36:02 dox kernel: Latency 19ms PID 0 % swapper > Jul 15 01:43:46 dox kernel: Latency 7ms PID 0 % swapper > > That is all above 5 ms two runs, compare that to the old one. > (a run = 3 * write 150 MB, 3 * copy 150 MB, > 3 * read 300 MB, 3 * diff 150 MB) > > kernel folks: > * Why do I get better latencies? > * Why does latencies get worse when enabling good options? > > /RogerL > > -- > Home page: > http://www.norran.net/nra02596/ > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu > Please read the FAQ at http://www.tux.org/lkml/
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