[PATCH] Increase MAX_STACK_TRACE_ENTRIES

[PATCH] Increase MAX_STACK_TRACE_ENTRIES

[John Kacur]

Ingo: please consider this patch if there are no negative consequences to 
increasing this value. It fixes a problem that we have seen in the past on
(at least) the real-time kernel. (BUG: MAX_STACK_TRACE_ENTRIES).

This patch applies to the current tip/master

Thank You

Author: Clark Williams <williams@redhat.com>
Date: Mon, 21 Sep 2009 18:29:30 +0200
Subject: [PATCH] Increase MAX_STACK_TRACE_ENTRIES to compensate for lockdep and debug options eating up backtrace slots.

    Signed-off-by: Clark Williams <williams@redhat.com>
    Signed-off-by: John Kacur <jkacur@redhat.com>
---
 kernel/lockdep_internals.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index a2ee95a..953745c 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -65,7 +65,7 @@ enum {
  * Stack-trace: tightly packed array of stack backtrace
  * addresses. Protected by the hash_lock.
  */
-#define MAX_STACK_TRACE_ENTRIES	262144UL
+#define MAX_STACK_TRACE_ENTRIES	393216UL
 
 extern struct list_head all_lock_classes;
 extern struct lock_chain lock_chains[];
-- 
1.6.0.6

Re: [PATCH] Increase MAX_STACK_TRACE_ENTRIES

[Peter Zijlstra]

On Mon, 2009-09-21 at 19:13 +0200, John Kacur wrote:
> Ingo: please consider this patch if there are no negative consequences to 
> increasing this value. It fixes a problem that we have seen in the past on
> (at least) the real-time kernel. (BUG: MAX_STACK_TRACE_ENTRIES).
> 
> This patch applies to the current tip/master

Hrmm,.. this is growing to be very large indeed.

It would be nice to know where all these extra entries are coming from.
How large are:

# cat /proc/lockdep | grep -v -e "\->" -e "^$" | wc -l
437

# cat /proc/lockdep | grep -v -e "\->" -e "^$" | awk '{print $6}' | 
                      tr -d ".:" | grep -v "^$" | wc -c
1031

On your machine?

> -#define MAX_STACK_TRACE_ENTRIES	262144UL
> +#define MAX_STACK_TRACE_ENTRIES	393216UL