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nova: remove timer delay heuristic 

The commit uses a fixed kernel branch (r8), which fixes a caching bug
observable in the Genode host. The quirk detecting the circumstance in the
timer service is obsolete now and is removed.

Fixes #1338
This commit is contained in:
Alexander Boettcher 2015-01-06 10:32:01 +01:00 committed by Christian Helmuth
parent 1d920fa1b5
commit 8842ba2e1c
3 changed files with 3 additions and 45 deletions
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2
repos/base-nova/ports/nova.hash
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@ -1 +1 @@
d5f067a88da045f9fc6f9adb0ce532de0d4c047c
0c75755a7d208d1f114b25becd129c760d57f456

4
repos/base-nova/ports/nova.port
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@ -3,8 +3,8 @@ VERSION := git
DOWNLOADS := nova.git
URL(nova) := https://github.com/alex-ab/NOVA.git
# r7 branch
REV(nova) := 2b4f2803218cf92e2982b47a370d60b18bb78a15
# r8 branch
REV(nova) := 41868231ae25678e1f2e344e40fbdbd0fd13e8ee
DIR(nova) := src/kernel/nova
PATCHES := $(wildcard $(REP_DIR)/patches/*.patch)

42
repos/os/src/drivers/timer/nova/platform_timer.h
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@ -99,13 +99,6 @@ class Platform_timer
using namespace Genode;
using namespace Nova;
/* XXX quirk start - description below */
static unsigned short quirk_count = 0;
static unsigned int delay = 0;
Trace::Timestamp before = Trace::timestamp();
asm volatile ("":::"memory");
/* XXX quirk end */
if (_sem == ~0UL)
_sem = blocking_thread->tid().exc_pt_sel + SM_SEL_EC;
@ -123,41 +116,6 @@ class Platform_timer
return;
}
/*
* XXX quirk start
*
* On some x86 platforms, it happens that the system seems to slow
* down dramatically for some unclear reasons so far. When this
* happens, the handling of the timeout queue and reprogramming the
* next timeout takes so long that the timer IRQ will fire
* immediately after acknowledging it. This causes the timer
* service to run on a very high rate, which may utilize the CPU
* close to the maximum. We try to detect this condition by the
* following heuristic and apply this quirk, which programs the
* next timeout later in time - so that it will fire not
* immediately after acknowledging it.
*
* This quirk should be removed as soon as it is clear what
* triggers the phenomenon.
*/
unsigned long diff = _time_in_us(now - before, false);
if (diff)
quirk_count++;
else {
quirk_count = 0;
delay = 0;
}
if (quirk_count > 10) {
delay += 10000;
us_64 += delay;
PWRN("apply timer quirk - diff=%lu, delay timeout %lu->%llu us",
diff, _timeout, us_64);
quirk_count = 0;
}
/* XXX quirk end */
/* block until timeout fires or it gets canceled */
unsigned long long tsc_absolute = now + us_64 * (_tsc_khz / TSC_FACTOR);
Genode::uint8_t res = sm_ctrl(sem, SEMAPHORE_DOWN, tsc_absolute);