From: Byungchul Park <byungchul.park@lge.com>
To: peterz@infradead.org, mingo@kernel.org
Cc: tglx@linutronix.de, walken@google.com, boqun.feng@gmail.com,
kirill@shutemov.name, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, iamjoonsoo.kim@lge.com,
akpm@linux-foundation.org, npiggin@gmail.com
Subject: [PATCH v3 01/15] x86/dumpstack: Optimize save_stack_trace
Date: Tue, 13 Sep 2016 18:45:00 +0900 [thread overview]
Message-ID: <1473759914-17003-2-git-send-email-byungchul.park@lge.com> (raw)
In-Reply-To: <1473759914-17003-1-git-send-email-byungchul.park@lge.com>
Currently, x86 implementation of save_stack_trace() is walking all stack
region word by word regardless of what the trace->max_entries is.
However, it's unnecessary to walk after already fulfilling caller's
requirement, say, if trace->nr_entries >= trace->max_entries is true.
I measured its overhead and printed its difference of sched_clock() with
my QEMU x86 machine. The latency was improved over 70% when
trace->max_entries = 5.
Before this patch:
[ 2.329573] save_stack_trace() takes 76820 ns
[ 2.329863] save_stack_trace() takes 62131 ns
[ 2.330000] save_stack_trace() takes 99476 ns
[ 2.329846] save_stack_trace() takes 62419 ns
[ 2.330000] save_stack_trace() takes 88918 ns
[ 2.330253] save_stack_trace() takes 73669 ns
[ 2.330520] save_stack_trace() takes 67876 ns
[ 2.330671] save_stack_trace() takes 75963 ns
[ 2.330983] save_stack_trace() takes 95079 ns
[ 2.330451] save_stack_trace() takes 62352 ns
After this patch:
[ 2.795000] save_stack_trace() takes 21147 ns
[ 2.795397] save_stack_trace() takes 20230 ns
[ 2.795397] save_stack_trace() takes 31274 ns
[ 2.795739] save_stack_trace() takes 19706 ns
[ 2.796484] save_stack_trace() takes 20266 ns
[ 2.796484] save_stack_trace() takes 20902 ns
[ 2.797000] save_stack_trace() takes 38110 ns
[ 2.797510] save_stack_trace() takes 20224 ns
[ 2.798181] save_stack_trace() takes 20172 ns
[ 2.798837] save_stack_trace() takes 20824 ns
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
arch/x86/include/asm/stacktrace.h | 1 +
arch/x86/kernel/dumpstack.c | 4 ++++
arch/x86/kernel/dumpstack_32.c | 2 ++
arch/x86/kernel/stacktrace.c | 7 +++++++
4 files changed, 14 insertions(+)
diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 0944218..f6d0694 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -41,6 +41,7 @@ struct stacktrace_ops {
/* On negative return stop dumping */
int (*stack)(void *data, char *name);
walk_stack_t walk_stack;
+ int (*end_walk)(void *data);
};
void dump_trace(struct task_struct *tsk, struct pt_regs *regs,
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index ef8017c..274d42a 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -113,6 +113,8 @@ print_context_stack(struct task_struct *task,
print_ftrace_graph_addr(addr, data, ops, task, graph);
}
stack++;
+ if (ops->end_walk && ops->end_walk(data))
+ break;
}
return bp;
}
@@ -138,6 +140,8 @@ print_context_stack_bp(struct task_struct *task,
frame = frame->next_frame;
ret_addr = &frame->return_address;
print_ftrace_graph_addr(addr, data, ops, task, graph);
+ if (ops->end_walk && ops->end_walk(data))
+ break;
}
return (unsigned long)frame;
diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index fef917e..762d1fd 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -69,6 +69,8 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
bp = ops->walk_stack(task, stack, bp, ops, data,
end_stack, &graph);
+ if (ops->end_walk && ops->end_walk(data))
+ break;
/* Stop if not on irq stack */
if (!end_stack)
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 9ee98ee..a44de4d 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -47,10 +47,17 @@ save_stack_address_nosched(void *data, unsigned long addr, int reliable)
return __save_stack_address(data, addr, reliable, true);
}
+static int save_stack_end(void *data)
+{
+ struct stack_trace *trace = data;
+ return trace->nr_entries >= trace->max_entries;
+}
+
static const struct stacktrace_ops save_stack_ops = {
.stack = save_stack_stack,
.address = save_stack_address,
.walk_stack = print_context_stack,
+ .end_walk = save_stack_end,
};
static const struct stacktrace_ops save_stack_ops_nosched = {
--
1.9.1
--
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next prev parent reply other threads:[~2016-09-13 9:48 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-13 9:44 [PATCH v3 00/15] lockdep: Implement crossrelease feature Byungchul Park
2016-09-13 9:45 ` Byungchul Park [this message]
2016-09-13 13:18 ` [PATCH v3 01/15] x86/dumpstack: Optimize save_stack_trace Josh Poimboeuf
2016-09-13 14:54 ` Byungchul Park
2016-09-13 9:45 ` [PATCH v3 02/15] x86/dumpstack: Add save_stack_trace()_fast() Byungchul Park
2016-09-13 13:20 ` Josh Poimboeuf
2016-09-13 9:45 ` [PATCH v3 03/15] lockdep: Refactor lookup_chain_cache() Byungchul Park
2016-09-15 15:33 ` Nilay Vaish
2016-09-19 3:05 ` Byungchul Park
2016-09-19 16:36 ` Nilay Vaish
2016-09-20 2:00 ` Byungchul Park
2016-09-13 9:45 ` [PATCH v3 04/15] lockdep: Add a function building a chain between two classes Byungchul Park
2016-09-13 9:45 ` [PATCH v3 05/15] lockdep: Make check_prev_add can use a separate stack_trace Byungchul Park
2016-09-13 9:45 ` [PATCH v3 06/15] lockdep: Make save_trace can skip stack tracing of the current Byungchul Park
2016-09-13 9:45 ` [PATCH v3 07/15] lockdep: Implement crossrelease feature Byungchul Park
2016-09-13 10:05 ` Peter Zijlstra
2016-09-13 12:09 ` Peter Zijlstra
2016-09-13 15:14 ` Byungchul Park
2016-09-13 15:05 ` Peter Zijlstra
2016-09-13 17:12 ` Byungchul Park
2016-09-13 19:38 ` Peter Zijlstra
2016-09-13 21:42 ` Peter Zijlstra
2016-09-14 1:01 ` Byungchul Park
2016-09-14 2:27 ` Byungchul Park
2016-09-14 4:49 ` Byungchul Park
2016-09-14 8:11 ` Peter Zijlstra
2016-09-19 2:41 ` Byungchul Park
2016-09-19 8:50 ` Peter Zijlstra
2016-09-20 5:50 ` Byungchul Park
2016-09-20 6:26 ` Byungchul Park
2016-09-21 1:37 ` Byungchul Park
2016-09-22 2:57 ` Byungchul Park
2016-09-13 9:45 ` [PATCH v3 08/15] lockdep: Make crossrelease use save_stack_trace_fast() Byungchul Park
2016-09-13 9:45 ` [PATCH v3 09/15] lockdep: Make print_circular_bug() crosslock-aware Byungchul Park
2016-09-13 9:45 ` [PATCH v3 10/15] lockdep: Apply crossrelease to completion operation Byungchul Park
2016-09-13 9:45 ` [PATCH v3 11/15] pagemap.h: Remove trailing white space Byungchul Park
2016-09-13 9:45 ` [PATCH v3 12/15] lockdep: Apply crossrelease to PG_locked lock Byungchul Park
2016-09-13 9:45 ` [PATCH v3 13/15] lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked Byungchul Park
2016-09-13 9:45 ` [PATCH v3 14/15] lockdep: Move data used in CONFIG_LOCKDEP_PAGELOCK from page to page_ext Byungchul Park
2016-09-13 9:45 ` [PATCH v3 15/15] lockdep: Crossrelease feature documentation Byungchul Park
2016-09-15 17:25 ` Nilay Vaish
2016-09-19 2:59 ` Byungchul Park
2016-09-16 15:47 ` Nilay Vaish
2016-09-19 3:00 ` Byungchul Park
2016-09-20 5:00 ` Byungchul Park
2016-09-13 9:58 ` [FYI] Output of 'cat /proc/lockdep' after applying crossrelease Byungchul Park
2016-11-02 5:42 ` [REVISED DOC on v3] Crossrelease Lockdep Byungchul Park
2016-11-03 8:18 ` Byungchul Park
2016-11-08 2:54 ` Byungchul Park
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