Messages in this thread | | | Date | Thu, 2 Dec 1999 11:53:45 -0500 (EST) | From | William Montgomery <> | Subject | Re: lowlatency-2.2.13-A1 questions |
| |
On Wed, 1 Dec 1999, Ingo Molnar wrote: > the 2.2.13 patches do not have the console changes - and text console > scrollback is introducing latencies around 4msec. The reason is that > occasionally the console driver has to read+copy the whole (text) > videoram, and this is slow. I solved this by adding a read-cache for all > videoram contents, thus videoram only ever has to be written. (which is > fast) > I patched my 2.2.13 kernel with 2.2.12-ikd7.bz2 and fixed the rejects, then I applied the lowlatency-2.2.13-A1 patch and fixed the rejects. All this works fine in my new kernel.
I set up a latency test program using the rtc device to interrupt at 64Hz. I am using the ktrace utility to examine the /proc/trace info after the latency test program releases a lock indicating a scheduling latency exceeding 5msec. I see a problem which appears to be unrelated to the console driver. When the "rtc_interrupt" occurs between the "schedule" and the "__switch_to" (apparently just prior to __switch_to) another pid is switched in and even though there are many "system_call"s the test program is held off ~5msec. Any ideas?
I think the lowlatency patch is a very useful and important enhancement to the kernel, will it become part of the mainstream kernel source (2.4.x)?
Wm
- 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/
| |