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um: Switch clocksource to hrtimers

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UML is using an obsolete itimer call for
all timers and "polls" for kernel space timer firing
in its userspace portion resulting in a long list
of bugs and incorrect behaviour(s). It also uses
ITIMER_VIRTUAL for its timer which results in the
timer being dependent on it running and the cpu
load.

This patch fixes this by moving to posix high resolution
timers firing off CLOCK_MONOTONIC and relaying the timer
correctly to the UML userspace.

Fixes:
 - crashes when hosts suspends/resumes
 - broken userspace timers - effecive ~40Hz instead
   of what they should be. Note - this modifies skas behavior
   by no longer setting an itimer per clone(). Timer events
   are relayed instead.
 - kernel network packet scheduling disciplines
 - tcp behaviour especially under load
 - various timer related corner cases

Finally, overall responsiveness of userspace is better.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Anton Ivanov <aivanov@brocade.com>
[rw: massaged commit message]
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Anton Ivanov
2015-11-02 16:16:37 +00:00
committed by Richard Weinberger
parent e17c6d77b2
commit 2eb5f31bc4
14 changed files with 280 additions and 249 deletions
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7
arch/um/include/shared/skas/stub-data.h
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@@ -1,4 +1,6 @@
/*
* Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
* Copyright (C) 2005 Jeff Dike (jdike@karaya.com)
* Licensed under the GPL
*/
@@ -6,12 +8,11 @@
#ifndef __STUB_DATA_H
#define __STUB_DATA_H
#include <sys/time.h>
#include <time.h>
struct stub_data {
long offset;
unsigned long offset;
int fd;
struct itimerval timer;
long err;
};