Linux 2.6.37-rc5-git2
This commit is contained in:
Kyle McMartin
parent
abce2aa994
commit
98e6119f39
1
.gitignore
vendored
1
.gitignore
vendored
@ -4,3 +4,4 @@ clog
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*.rpm
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kernel-2.6.*/
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/patch-2.6.37-rc5.bz2
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/patch-2.6.37-rc5-git2.bz2
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10
kernel.spec
10
kernel.spec
@ -84,7 +84,7 @@ Summary: The Linux kernel
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# The rc snapshot level
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%define rcrev 5
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# The git snapshot level
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%define gitrev 0
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%define gitrev 2
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# Set rpm version accordingly
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%define rpmversion 2.6.%{upstream_sublevel}
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%endif
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@ -706,6 +706,9 @@ Patch12401: debug-tty-print-dev-name.patch
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Patch12410: mm-page-allocator-adjust-the-per-cpu-counter-threshold-when-memory-is-low.patch
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Patch12411: mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds.patch
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# rhbz#650934
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Patch12420: sched-cure-more-NO_HZ-load-average-woes.patch
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%endif
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BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
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@ -1915,6 +1918,11 @@ fi
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# || ||
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%changelog
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* Wed Dec 08 2010 Kyle McMartin <kyle@redhat.com> 2.6.37-0.rc5.git2.1
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- Linux 2.6.37-rc5-git2
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- sched-cure-more-NO_HZ-load-average-woes.patch: fix some of the complaints
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in 2.6.35+ about load average with dynticks. (rhbz#650934)
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* Tue Dec 07 2010 Kyle McMartin <kyle@redhat.com> 2.6.37-0.rc5.git0.1
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- Linux 2.6.37-rc5
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273
sched-cure-more-NO_HZ-load-average-woes.patch
Normal file
273
sched-cure-more-NO_HZ-load-average-woes.patch
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@ -0,0 +1,273 @@
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From bounces.tip@hpa.at.zytor.com Wed Dec 8 15:40:48 2010
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From: tip-bot for Peter Zijlstra <a.p.zijlstra@chello.nl>
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In-Reply-To: <1291129145.32004.874.camel@laptop>
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References: <1291129145.32004.874.camel@laptop>
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Subject: [tip:sched/urgent] sched: Cure more NO_HZ load average woes
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Message-ID: <tip-0f004f5a696a9434b7214d0d3cbd0525ee77d428@git.kernel.org>
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Git-Commit-ID: 0f004f5a696a9434b7214d0d3cbd0525ee77d428
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Commit-ID: 0f004f5a696a9434b7214d0d3cbd0525ee77d428
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Gitweb: http://git.kernel.org/tip/0f004f5a696a9434b7214d0d3cbd0525ee77d428
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Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
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AuthorDate: Tue, 30 Nov 2010 19:48:45 +0100
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Committer: Ingo Molnar <mingo@elte.hu>
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CommitDate: Wed, 8 Dec 2010 20:15:04 +0100
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sched: Cure more NO_HZ load average woes
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There's a long-running regression that proved difficult to fix and
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which is hitting certain people and is rather annoying in its effects.
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Damien reported that after 74f5187ac8 (sched: Cure load average vs
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NO_HZ woes) his load average is unnaturally high, he also noted that
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even with that patch reverted the load avgerage numbers are not
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correct.
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The problem is that the previous patch only solved half the NO_HZ
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problem, it addressed the part of going into NO_HZ mode, not of
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comming out of NO_HZ mode. This patch implements that missing half.
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When comming out of NO_HZ mode there are two important things to take
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care of:
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- Folding the pending idle delta into the global active count.
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- Correctly aging the averages for the idle-duration.
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So with this patch the NO_HZ interaction should be complete and
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behaviour between CONFIG_NO_HZ=[yn] should be equivalent.
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Furthermore, this patch slightly changes the load average computation
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by adding a rounding term to the fixed point multiplication.
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Reported-by: Damien Wyart <damien.wyart@free.fr>
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Reported-by: Tim McGrath <tmhikaru@gmail.com>
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Tested-by: Damien Wyart <damien.wyart@free.fr>
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Tested-by: Orion Poplawski <orion@cora.nwra.com>
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Tested-by: Kyle McMartin <kyle@mcmartin.ca>
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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Cc: stable@kernel.org
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Cc: Chase Douglas <chase.douglas@canonical.com>
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LKML-Reference: <1291129145.32004.874.camel@laptop>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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---
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include/linux/sched.h | 2 +-
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kernel/sched.c | 150 +++++++++++++++++++++++++++++++++++++++++++++----
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kernel/timer.c | 2 +-
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3 files changed, 141 insertions(+), 13 deletions(-)
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diff --git a/include/linux/sched.h b/include/linux/sched.h
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index 2c79e92..2238745 100644
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -143,7 +143,7 @@ extern unsigned long nr_iowait_cpu(int cpu);
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extern unsigned long this_cpu_load(void);
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-extern void calc_global_load(void);
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+extern void calc_global_load(unsigned long ticks);
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extern unsigned long get_parent_ip(unsigned long addr);
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diff --git a/kernel/sched.c b/kernel/sched.c
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index dc91a4d..6b7c26a 100644
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--- a/kernel/sched.c
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+++ b/kernel/sched.c
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@@ -3119,6 +3119,15 @@ static long calc_load_fold_active(struct rq *this_rq)
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return delta;
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}
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+static unsigned long
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+calc_load(unsigned long load, unsigned long exp, unsigned long active)
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+{
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+ load *= exp;
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+ load += active * (FIXED_1 - exp);
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+ load += 1UL << (FSHIFT - 1);
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+ return load >> FSHIFT;
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+}
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+
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#ifdef CONFIG_NO_HZ
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/*
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* For NO_HZ we delay the active fold to the next LOAD_FREQ update.
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@@ -3148,6 +3157,128 @@ static long calc_load_fold_idle(void)
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return delta;
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}
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+
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+/**
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+ * fixed_power_int - compute: x^n, in O(log n) time
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+ *
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+ * @x: base of the power
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+ * @frac_bits: fractional bits of @x
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+ * @n: power to raise @x to.
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+ *
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+ * By exploiting the relation between the definition of the natural power
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+ * function: x^n := x*x*...*x (x multiplied by itself for n times), and
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+ * the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,
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+ * (where: n_i \elem {0, 1}, the binary vector representing n),
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+ * we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is
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+ * of course trivially computable in O(log_2 n), the length of our binary
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+ * vector.
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+ */
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+static unsigned long
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+fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
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+{
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+ unsigned long result = 1UL << frac_bits;
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+
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+ if (n) for (;;) {
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+ if (n & 1) {
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+ result *= x;
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+ result += 1UL << (frac_bits - 1);
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+ result >>= frac_bits;
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+ }
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+ n >>= 1;
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+ if (!n)
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+ break;
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+ x *= x;
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+ x += 1UL << (frac_bits - 1);
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+ x >>= frac_bits;
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+ }
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+
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+ return result;
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+}
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+
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+/*
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+ * a1 = a0 * e + a * (1 - e)
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+ *
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+ * a2 = a1 * e + a * (1 - e)
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+ * = (a0 * e + a * (1 - e)) * e + a * (1 - e)
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+ * = a0 * e^2 + a * (1 - e) * (1 + e)
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+ *
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+ * a3 = a2 * e + a * (1 - e)
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+ * = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)
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+ * = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
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+ *
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+ * ...
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+ *
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+ * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]
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+ * = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)
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+ * = a0 * e^n + a * (1 - e^n)
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+ *
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+ * [1] application of the geometric series:
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+ *
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+ * n 1 - x^(n+1)
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+ * S_n := \Sum x^i = -------------
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+ * i=0 1 - x
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+ */
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+static unsigned long
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+calc_load_n(unsigned long load, unsigned long exp,
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+ unsigned long active, unsigned int n)
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+{
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+
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+ return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
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+}
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+
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+/*
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+ * NO_HZ can leave us missing all per-cpu ticks calling
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+ * calc_load_account_active(), but since an idle CPU folds its delta into
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+ * calc_load_tasks_idle per calc_load_account_idle(), all we need to do is fold
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+ * in the pending idle delta if our idle period crossed a load cycle boundary.
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+ *
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+ * Once we've updated the global active value, we need to apply the exponential
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+ * weights adjusted to the number of cycles missed.
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+ */
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+static void calc_global_nohz(unsigned long ticks)
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+{
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+ long delta, active, n;
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+
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+ if (time_before(jiffies, calc_load_update))
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+ return;
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+
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+ /*
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+ * If we crossed a calc_load_update boundary, make sure to fold
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+ * any pending idle changes, the respective CPUs might have
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+ * missed the tick driven calc_load_account_active() update
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+ * due to NO_HZ.
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+ */
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+ delta = calc_load_fold_idle();
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+ if (delta)
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+ atomic_long_add(delta, &calc_load_tasks);
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+
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+ /*
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+ * If we were idle for multiple load cycles, apply them.
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+ */
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+ if (ticks >= LOAD_FREQ) {
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+ n = ticks / LOAD_FREQ;
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+
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+ active = atomic_long_read(&calc_load_tasks);
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+ active = active > 0 ? active * FIXED_1 : 0;
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+
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+ avenrun[0] = calc_load_n(avenrun[0], EXP_1, active, n);
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+ avenrun[1] = calc_load_n(avenrun[1], EXP_5, active, n);
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+ avenrun[2] = calc_load_n(avenrun[2], EXP_15, active, n);
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+
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+ calc_load_update += n * LOAD_FREQ;
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+ }
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+
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+ /*
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+ * Its possible the remainder of the above division also crosses
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+ * a LOAD_FREQ period, the regular check in calc_global_load()
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+ * which comes after this will take care of that.
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+ *
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+ * Consider us being 11 ticks before a cycle completion, and us
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+ * sleeping for 4*LOAD_FREQ + 22 ticks, then the above code will
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+ * age us 4 cycles, and the test in calc_global_load() will
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+ * pick up the final one.
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+ */
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+}
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#else
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static void calc_load_account_idle(struct rq *this_rq)
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{
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@@ -3157,6 +3288,10 @@ static inline long calc_load_fold_idle(void)
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{
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return 0;
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}
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+
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+static void calc_global_nohz(unsigned long ticks)
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+{
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+}
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#endif
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/**
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@@ -3174,24 +3309,17 @@ void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
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loads[2] = (avenrun[2] + offset) << shift;
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}
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-static unsigned long
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-calc_load(unsigned long load, unsigned long exp, unsigned long active)
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-{
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- load *= exp;
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- load += active * (FIXED_1 - exp);
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- return load >> FSHIFT;
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-}
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-
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/*
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* calc_load - update the avenrun load estimates 10 ticks after the
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* CPUs have updated calc_load_tasks.
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*/
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-void calc_global_load(void)
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+void calc_global_load(unsigned long ticks)
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{
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- unsigned long upd = calc_load_update + 10;
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long active;
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- if (time_before(jiffies, upd))
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+ calc_global_nohz(ticks);
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+
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+ if (time_before(jiffies, calc_load_update + 10))
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return;
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active = atomic_long_read(&calc_load_tasks);
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diff --git a/kernel/timer.c b/kernel/timer.c
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index 68a9ae7..7bd715f 100644
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--- a/kernel/timer.c
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+++ b/kernel/timer.c
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@@ -1319,7 +1319,7 @@ void do_timer(unsigned long ticks)
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{
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jiffies_64 += ticks;
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update_wall_time();
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- calc_global_load();
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+ calc_global_load(ticks);
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}
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#ifdef __ARCH_WANT_SYS_ALARM
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