-----Original Message-----
 From: Olivier Matz [mailto:olivier.matz@6wind.com]
 Sent: Friday, March 24, 2017 9:05 AM
 To: Eads, Gage [off-list ref]
 Cc: dev@dpdk.org
 Subject: Re: [PATCH v3] mempool: remove non-EAL thread note from header
 
 Hi Gage,
 
 On Thu, 23 Mar 2017 09:20:58 -0500, Gage Eads [off-list ref]
 wrote:
 > Commit 30e6399892276 ("mempool: support non-EAL thread") added the
 > capability for non-EAL threads to use the mempool library. This commit
 > removes the note indicating that the mempool library cannot be used
 > safely by non-EAL threads.
 >
 > Also, fix a typo.
 >
 > Signed-off-by: Gage Eads [off-list ref]
 > ---
 > v2: Changed commit message to referenced commit 30e63998 instead of
 > 4b5062755
 > v3: Fix checkpatch error
 >
 >  lib/librte_mempool/rte_mempool.h | 6 +-----
 >  1 file changed, 1 insertion(+), 5 deletions(-)
 >
 > diff --git a/lib/librte_mempool/rte_mempool.h
 > b/lib/librte_mempool/rte_mempool.h
 > index 991feaa..b1186fd 100644
 > --- a/lib/librte_mempool/rte_mempool.h
 > +++ b/lib/librte_mempool/rte_mempool.h
 > @@ -53,11 +53,7 @@
 >   *
 >   * Note: the mempool implementation is not preemptable. A lcore must
 >   * not be interrupted by another task that uses the same mempool
 > - * (because it uses a ring which is not preemptable). Also, mempool
 > - * functions must not be used outside the DPDK environment: for
 > - * example, in linuxapp environment, a thread that is not created by
 > - * the EAL must not use mempools. This is due to the per-lcore cache
 > - * that won't work as rte_lcore_id() will not return a correct value.
 > + * (because it uses a ring which is not preemptible).
 >   */
 >
 >  #include <stdio.h>
 
 I agree the comment is not correct today. But I think we should still highlight
 that usual functions [ex: rte_mempool_get(), rte_mempool_put()] won't work
 when called on a non-EAL thread.

My understanding is that non-EAL threads can call those functions, but their performance will suffer since they go directly to the underlying ring. Is that correct?

 
 Maybe it could be reworded in that way:
 
 """
 Note: the mempool implementation is not preemptable. A lcore must not be
 interrupted by another task that uses the same mempool (because it uses a ring
 which is not preemptible). Also, usual mempool functions like
 rte_mempool_get() or rte_mempool_put() are designed to be called from an
 EAL thread due to the internal per-lcore cache. When using a mempool from a
 non-EAL thread, a user cache has to be provided to
 rte_mempool_generic_get() or rte_mempool_generic_put().
 """
 
 What do you think?

Agreed, this looks better. If indeed non-EAL threads can call rte_mempool_get() and _put(), perhaps the last sentence can be reworked like so?

Due to the lack of caching, rte_mempool_get() or rte_mempool_put() performance
will suffer when called by non-EAL threads. Instead, non-EAL threads should call
rte_mempool_generic_get() or rte_mempool_generic_put() with a user cache
created with rte_mempool_cache_create().

 
 Thanks,
 Olivier