[PATCH] ftrace: Do not copy old hash when resetting.

[PATCH] ftrace: Do not copy old hash when resetting.

[Wang Nan]

If we are going to reset hash, we don't need to duplicate old hash
and remove every entries right after allocation.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
---
 kernel/trace/ftrace.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5b372e3..52d6931 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3471,14 +3471,16 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
 	else
 		orig_hash = &ops->notrace_hash;
 
-	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
+	if (!reset)
+		hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
+	else
+		hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
+
 	if (!hash) {
 		ret = -ENOMEM;
 		goto out_regex_unlock;
 	}
 
-	if (reset)
-		ftrace_filter_reset(hash);
 	if (buf && !ftrace_match_records(hash, buf, len)) {
 		ret = -EINVAL;
 		goto out_regex_unlock;
-- 
1.8.4

Re: [PATCH] ftrace: Do not copy old hash when resetting.

[Steven Rostedt]

On Mon, 14 Jul 2014 12:10:00 +0800
Wang Nan <wangnan0@huawei.com> wrote:

> If we are going to reset hash, we don't need to duplicate old hash
> and remove every entries right after allocation.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> ---
>  kernel/trace/ftrace.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 5b372e3..52d6931 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3471,14 +3471,16 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
>  	else
>  		orig_hash = &ops->notrace_hash;
>  
> -	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
> +	if (!reset)
> +		hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
> +	else
> +		hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);

I'm fine with this patch, but please swap the if statement above. I
prefer the if condition being positive if there's also an else
statement above. That is:

	if (reset)
		hash = alloc_ftrace_hash();
	else
		hash = alloc_and_copy_ftrace_hash();

-- Steve

> +
>  	if (!hash) {
>  		ret = -ENOMEM;
>  		goto out_regex_unlock;
>  	}
>  
> -	if (reset)
> -		ftrace_filter_reset(hash);
>  	if (buf && !ftrace_match_records(hash, buf, len)) {
>  		ret = -EINVAL;
>  		goto out_regex_unlock;

Re: [PATCH] ftrace: Do not copy old hash when resetting.

[Wang Nan]

Hi Steve,

What's your opinion on my v2 patch ( https://lkml.org/lkml/2014/7/14/839 )?

I have swapped if consitions following your suggestion.

On 2014/7/14 12:10, Wang Nan wrote:
> If we are going to reset hash, we don't need to duplicate old hash
> and remove every entries right after allocation.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> ---
>  kernel/trace/ftrace.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 5b372e3..52d6931 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3471,14 +3471,16 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
>  	else
>  		orig_hash = &ops->notrace_hash;
>  
> -	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
> +	if (!reset)
> +		hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
> +	else
> +		hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
> +
>  	if (!hash) {
>  		ret = -ENOMEM;
>  		goto out_regex_unlock;
>  	}
>  
> -	if (reset)
> -		ftrace_filter_reset(hash);
>  	if (buf && !ftrace_match_records(hash, buf, len)) {
>  		ret = -EINVAL;
>  		goto out_regex_unlock;
> 

Re: [PATCH] ftrace: Do not copy old hash when resetting.

[Steven Rostedt]

On Fri, 18 Jul 2014 12:44:18 +0800
Wang Nan <wangnan0@huawei.com> wrote:

> Hi Steve,
> 
> What's your opinion on my v2 patch ( https://lkml.org/lkml/2014/7/14/839 )?
> 
> I have swapped if consitions following your suggestion.
> 

Bah I didn't see it.

Damn Claws mail, I need to figure out why the f*ck it randomly marks
all my email as read. This has caused me to miss a few important emails
recently :-(

It looks fine, I've now marked it as todo that way I'll see it to pull
it in for 3.17. Thanks,

-- Steve


> On 2014/7/14 12:10, Wang Nan wrote:
> > If we are going to reset hash, we don't need to duplicate old hash
> > and remove every entries right after allocation.
> > 
> > Signed-off-by: Wang Nan <wangnan0@huawei.com>
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > ---
> >  kernel/trace/ftrace.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 5b372e3..52d6931 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -3471,14 +3471,16 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
> >  	else
> >  		orig_hash = &ops->notrace_hash;
> >  
> > -	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
> > +	if (!reset)
> > +		hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
> > +	else
> > +		hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
> > +
> >  	if (!hash) {
> >  		ret = -ENOMEM;
> >  		goto out_regex_unlock;
> >  	}
> >  
> > -	if (reset)
> > -		ftrace_filter_reset(hash);
> >  	if (buf && !ftrace_match_records(hash, buf, len)) {
> >  		ret = -EINVAL;
> >  		goto out_regex_unlock;
> > 
>