[PATCH] CodeSamples/defer: Make hazard partition consistent with hazptr_thread_exit

[PATCH] CodeSamples/defer: Make hazard partition consistent with hazptr_thread_exit

[Alan Huang]

Signed-off-by: Alan Huang <mmpgouride@gmail.com>
---
 CodeSamples/defer/hazptrtorture.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CodeSamples/defer/hazptrtorture.h b/CodeSamples/defer/hazptrtorture.h
index 29761e3d..acdd532b 100644
--- a/CodeSamples/defer/hazptrtorture.h
+++ b/CodeSamples/defer/hazptrtorture.h
@@ -99,7 +99,7 @@ void *hazptr_read_perf_test(void *arg)
 {
 	int i;
 	int me = (long)arg;
-	int base = me * K;
+	int base = smp_thread_id() * K;
 	long long n_reads_local = 0;
 	hazptr_head_t hh;
 	hazptr_head_t *hhp = &hh;
-- 
2.34.1

Re: [PATCH] CodeSamples/defer: Make hazard partition consistent with hazptr_thread_exit

[Paul E. McKenney]

On Thu, Apr 20, 2023 at 07:40:30AM +0000, Alan Huang wrote:
> Signed-off-by: Alan Huang <mmpgouride@gmail.com>
> ---
>  CodeSamples/defer/hazptrtorture.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/CodeSamples/defer/hazptrtorture.h b/CodeSamples/defer/hazptrtorture.h
> index 29761e3d..acdd532b 100644
> --- a/CodeSamples/defer/hazptrtorture.h
> +++ b/CodeSamples/defer/hazptrtorture.h
> @@ -99,7 +99,7 @@ void *hazptr_read_perf_test(void *arg)
>  {
>  	int i;
>  	int me = (long)arg;
> -	int base = me * K;
> +	int base = smp_thread_id() * K;

Suppose specify a number of threads greater than the number of CPUs.
For example, on my 12-hardware-thread laptop:

./route_hazptr --stresstest --nreaders 24

In that case, don't we want "me" rather than "smp_thread_id()"?

							Thanx, Paul

>  	long long n_reads_local = 0;
>  	hazptr_head_t hh;
>  	hazptr_head_t *hhp = &hh;
> -- 
> 2.34.1
> 

Re: [PATCH] CodeSamples/defer: Make hazard partition consistent with hazptr_thread_exit

[Akira Yokosawa]

On Mon, 24 Apr 2023 09:02:57 -0700, Paul E. McKenney wrote:
> On Thu, Apr 20, 2023 at 07:40:30AM +0000, Alan Huang wrote:
>> Signed-off-by: Alan Huang <mmpgouride@gmail.com>
>> ---
>>  CodeSamples/defer/hazptrtorture.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/CodeSamples/defer/hazptrtorture.h b/CodeSamples/defer/hazptrtorture.h
>> index 29761e3d..acdd532b 100644
>> --- a/CodeSamples/defer/hazptrtorture.h
>> +++ b/CodeSamples/defer/hazptrtorture.h
>> @@ -99,7 +99,7 @@ void *hazptr_read_perf_test(void *arg)
>>  {
>>  	int i;
>>  	int me = (long)arg;
>> -	int base = me * K;
>> +	int base = smp_thread_id() * K;
> 
> Suppose specify a number of threads greater than the number of CPUs.
> For example, on my 12-hardware-thread laptop:
> 
> ./route_hazptr --stresstest --nreaders 24
> 
> In that case, don't we want "me" rather than "smp_thread_id()"?

But route_hazptr.c includes routetorture.h
Furthermore, route_hazptr.c doesn't call hp_record() which just
got fixed.

So it looks to me that Alan's fixes won't have any effect on
route_hazptr ...

But I might be missing something here.

        Thanks, Akira

> 
> 							Thanx, Paul
> 
>>  	long long n_reads_local = 0;
>>  	hazptr_head_t hh;
>>  	hazptr_head_t *hhp = &hh;
>> -- 
>> 2.34.1
>>

Re: [PATCH] CodeSamples/defer: Make hazard partition consistent with hazptr_thread_exit

[Alan Huang]

> 2023年4月25日 00:02，Paul E. McKenney <paulmck@kernel.org> 写道：
> 
> On Thu, Apr 20, 2023 at 07:40:30AM +0000, Alan Huang wrote:
>> Signed-off-by: Alan Huang <mmpgouride@gmail.com>
>> ---
>> CodeSamples/defer/hazptrtorture.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/CodeSamples/defer/hazptrtorture.h b/CodeSamples/defer/hazptrtorture.h
>> index 29761e3d..acdd532b 100644
>> --- a/CodeSamples/defer/hazptrtorture.h
>> +++ b/CodeSamples/defer/hazptrtorture.h
>> @@ -99,7 +99,7 @@ void *hazptr_read_perf_test(void *arg)
>> {
>> 	int i;
>> 	int me = (long)arg;
>> -	int base = me * K;
>> +	int base = smp_thread_id() * K;
> 
> Suppose specify a number of threads greater than the number of CPUs.
> For example, on my 12-hardware-thread laptop:
> 
> ./route_hazptr --stresstest --nreaders 24
> 
> In that case, don't we want "me" rather than "smp_thread_id()"?

As Akira said, route_hazptr.c includes routetorture.h and route_hazptr.c doesn't call hp_record().
The fix won't have any effect on route_hazptr.

Thanks,
Alan

> 
> 							Thanx, Paul
> 
>> 	long long n_reads_local = 0;
>> 	hazptr_head_t hh;
>> 	hazptr_head_t *hhp = &hh;
>> -- 
>> 2.34.1
>> 

Re: [PATCH] CodeSamples/defer: Make hazard partition consistent with hazptr_thread_exit

[Paul E. McKenney]

On Tue, Apr 25, 2023 at 09:32:46PM +0800, Alan Huang wrote:
> > 2023年4月25日 00:02，Paul E. McKenney <paulmck@kernel.org> 写道：
> > 
> > On Thu, Apr 20, 2023 at 07:40:30AM +0000, Alan Huang wrote:
> >> Signed-off-by: Alan Huang <mmpgouride@gmail.com>
> >> ---
> >> CodeSamples/defer/hazptrtorture.h | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >> 
> >> diff --git a/CodeSamples/defer/hazptrtorture.h b/CodeSamples/defer/hazptrtorture.h
> >> index 29761e3d..acdd532b 100644
> >> --- a/CodeSamples/defer/hazptrtorture.h
> >> +++ b/CodeSamples/defer/hazptrtorture.h
> >> @@ -99,7 +99,7 @@ void *hazptr_read_perf_test(void *arg)
> >> {
> >> 	int i;
> >> 	int me = (long)arg;
> >> -	int base = me * K;
> >> +	int base = smp_thread_id() * K;
> > 
> > Suppose specify a number of threads greater than the number of CPUs.
> > For example, on my 12-hardware-thread laptop:
> > 
> > ./route_hazptr --stresstest --nreaders 24
> > 
> > In that case, don't we want "me" rather than "smp_thread_id()"?

Never mind, I was confused.  Maybe I should have waited another
day after return before looking at this.  :-/

$ ./hazptr 24 perf
sched_setaffinity: Invalid argument
Aborted (core dumped)

But that is a pre-existing problem.  If I keep the number within the
number of hardware threads, it works fine:

$ ./hazptr 12 perf
n_reads: 576608000  n_updates: 314343  nreaders: 12  nupdaters: 1 duration: 1
ns/read: 20.8114  ns/update: 3181.24

I am not all that worried about this.  Running multiple threads per
hardware thread in a performance test isn't all that useful, after all.
And there is a robust diagnostic.  Perhaps not as helpful as one might
like, but definitely robust.  ;-)

> As Akira said, route_hazptr.c includes routetorture.h and route_hazptr.c doesn't call hp_record().
> The fix won't have any effect on route_hazptr.

Agreed, again, my post-vacation confusion, apologies!!!

							Thanx, Paul