Messages in this thread |  | | Date | Tue, 27 Nov 2001 09:12:13 -0800 | From | Andrew Morton <> | Subject | Re: Unresponiveness of 2.4.16 |
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Ahmed Masud wrote: > > Just to add to the above something I've experienced: > > 2.4.12 - 2.4.14 on a number of AMD Athelon 900 with 256 MB > RAM doing serial I/O would miss data while any DISK writes would > occure.
Two possibilities suggest themselves:
- Interrupt latency. Last time I checked (a year ago), the worst-case interrupt latency of the IDE drivers was 80 microseconds on a 500MHz PII. That was with `hdparm -u 1'. That's pretty good.
Could you please confirm that you're using `hdparm -u 1' against the relevant disk?
- The serial port is working OK, but the application which is handling serial IO is blocked on a disk read (something got paged out), and that disk read fails to complete by the time the serial port buffer fills up.
I'll send you a patch which makes the VM less inclined to page things out in the presence of heavy writes, and which decreases read latencies.
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