diff mbox series

[4/4] mempool: use lcore API to check if lcore ID is valid

Message ID 20230309045738.1261000-5-honnappa.nagarahalli@arm.com (mailing list archive)
State New
Delegated to: Thomas Monjalon
Headers
Series Small corrections in mempool |

Checks

Context Check Description
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ci/loongarch-unit-testing fail Unit Testing FAIL
ci/Intel-compilation success Compilation OK
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ci/iol-intel-Performance success Performance Testing PASS
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Commit Message

Honnappa Nagarahalli March 9, 2023, 4:57 a.m. UTC 
  Use lcore API to check if the lcore ID is valid. The runtime
check does not add much value. Hence use assert to validate
the lcore ID.

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 lib/mempool/rte_mempool.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Comments

Konstantin Ananyev March 9, 2023, 9:39 a.m. UTC | #1 
> 
> Use lcore API to check if the lcore ID is valid. The runtime
> check does not add much value.

From my perspective it adds a perfect value:
Only threads with valid lcore id have their own default mempool cache.

> Hence use assert to validate
> the lcore ID.

Wonder why?
What's wrong for the thread to try to get default mempool cache?
That would change existing behavior and in general seems wrong to me.  
So I am strongly opposed.
 
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>  lib/mempool/rte_mempool.h | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
> index 009bd10215..00c5aa961b 100644
> --- a/lib/mempool/rte_mempool.h
> +++ b/lib/mempool/rte_mempool.h
> @@ -1314,10 +1314,9 @@ rte_mempool_cache_free(struct rte_mempool_cache *cache);
>  static __rte_always_inline struct rte_mempool_cache *
>  rte_mempool_default_cache(struct rte_mempool *mp, unsigned lcore_id)
>  {
> -	if (mp->cache_size == 0)
> -		return NULL;
> +	RTE_ASSERT(rte_lcore_id_is_valid(lcore_id));
> 
> -	if (lcore_id >= RTE_MAX_LCORE)
> +	if (mp->cache_size == 0)
>  		return NULL;
> 
>  	rte_mempool_trace_default_cache(mp, lcore_id,
> --
> 2.25.1
>
Honnappa Nagarahalli March 10, 2023, 4:01 a.m. UTC | #2 
<snip>
> 
> 
> 
> >
> > Use lcore API to check if the lcore ID is valid. The runtime check
> > does not add much value.
> 
> From my perspective it adds a perfect value:
> Only threads with valid lcore id have their own default mempool cache.
The threads would call 'rte_lcore_id()' to return their lcore_id. This ensures the lcore_id is valid already. Why do we need to check it again in rte_mempool_default_cache? Why would a thread use an incorrect lcore_id?

> 
> > Hence use assert to validate
> > the lcore ID.
> 
> Wonder why?
> What's wrong for the thread to try to get default mempool cache?
What are the cases where a thread does not know that it is not an EAL thread and call rte_mempool_default_cache with a random lcore_id?
Since, this API is called in the data plane, it makes sense to remove any additional validations.

> That would change existing behavior and in general seems wrong to me.
Agree on the change in existing behavior. We can discuss this once we agree/disagree on the above.

> So I am strongly opposed.
> 
> > Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > Reviewed-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > ---
> >  lib/mempool/rte_mempool.h | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
> > index 009bd10215..00c5aa961b 100644
> > --- a/lib/mempool/rte_mempool.h
> > +++ b/lib/mempool/rte_mempool.h
> > @@ -1314,10 +1314,9 @@ rte_mempool_cache_free(struct
> rte_mempool_cache
> > *cache);  static __rte_always_inline struct rte_mempool_cache *
> > rte_mempool_default_cache(struct rte_mempool *mp, unsigned lcore_id)
> > {
> > -	if (mp->cache_size == 0)
> > -		return NULL;
> > +	RTE_ASSERT(rte_lcore_id_is_valid(lcore_id));
> >
> > -	if (lcore_id >= RTE_MAX_LCORE)
> > +	if (mp->cache_size == 0)
> >  		return NULL;
> >
> >  	rte_mempool_trace_default_cache(mp, lcore_id,
> > --
> > 2.25.1
> >
Konstantin Ananyev March 10, 2023, 2:06 p.m. UTC | #3 
> 
> <snip>
> >
> >
> >
> > >
> > > Use lcore API to check if the lcore ID is valid. The runtime check
> > > does not add much value.
> >
> > From my perspective it adds a perfect value:
> > Only threads with valid lcore id have their own default mempool cache.
> The threads would call 'rte_lcore_id()' to return their lcore_id. This ensures the lcore_id is valid already.
> Why do we need to check it
> again in rte_mempool_default_cache? Why would a thread use an incorrect lcore_id?

rte_lcore_id() will just return you value of per-thread variable: RTE_PER_LCORE(_lcore_id).
Without any checking. For non-eal tthreads this value would be UINT32_MAX.
 
> >
> > > Hence use assert to validate
> > > the lcore ID.
> >
> > Wonder why?
> > What's wrong for the thread to try to get default mempool cache?
> What are the cases where a thread does not know that it is not an EAL thread and call rte_mempool_default_cache with a random
> lcore_id?
> Since, this API is called in the data plane, it makes sense to remove any additional validations.

Why is that?
I believe this API have to be generic and safe to call from any thread.
Let's look for example at:
*/
static __rte_always_inline void
rte_mempool_put_bulk(struct rte_mempool *mp, void * const *obj_table,
                     unsigned int n)
{
        struct rte_mempool_cache *cache;
        cache = rte_mempool_default_cache(mp, rte_lcore_id());
        rte_mempool_trace_put_bulk(mp, obj_table, n, cache);
        rte_mempool_generic_put(mp, obj_table, n, cache);
} 

Right now it is perfectly valid to invoke it from any thread.
With the change you propose invoking mempool_put() from non-EAL thread
will cause either a crash or silent memory corruption.
 
> > That would change existing behavior and in general seems wrong to me.
> Agree on the change in existing behavior. We can discuss this once we agree/disagree on the above.
> 
> > So I am strongly opposed.
> >
> > > Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > > Reviewed-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
> > > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > > ---
> > >  lib/mempool/rte_mempool.h | 5 ++---
> > >  1 file changed, 2 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
> > > index 009bd10215..00c5aa961b 100644
> > > --- a/lib/mempool/rte_mempool.h
> > > +++ b/lib/mempool/rte_mempool.h
> > > @@ -1314,10 +1314,9 @@ rte_mempool_cache_free(struct
> > rte_mempool_cache
> > > *cache);  static __rte_always_inline struct rte_mempool_cache *
> > > rte_mempool_default_cache(struct rte_mempool *mp, unsigned lcore_id)
> > > {
> > > -	if (mp->cache_size == 0)
> > > -		return NULL;
> > > +	RTE_ASSERT(rte_lcore_id_is_valid(lcore_id));
> > >
> > > -	if (lcore_id >= RTE_MAX_LCORE)
> > > +	if (mp->cache_size == 0)
> > >  		return NULL;
> > >
> > >  	rte_mempool_trace_default_cache(mp, lcore_id,
> > > --
> > > 2.25.1
> > >
diff mbox series

Patch

diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
index 009bd10215..00c5aa961b 100644
--- a/lib/mempool/rte_mempool.h
+++ b/lib/mempool/rte_mempool.h
@@ -1314,10 +1314,9 @@  rte_mempool_cache_free(struct rte_mempool_cache *cache);
 static __rte_always_inline struct rte_mempool_cache *
 rte_mempool_default_cache(struct rte_mempool *mp, unsigned lcore_id)
 {
-	if (mp->cache_size == 0)
-		return NULL;
+	RTE_ASSERT(rte_lcore_id_is_valid(lcore_id));
 
-	if (lcore_id >= RTE_MAX_LCORE)
+	if (mp->cache_size == 0)
 		return NULL;
 
 	rte_mempool_trace_default_cache(mp, lcore_id,