linux-kernel - Re: [PATCH 23/94] radix tree test suite: Add support for kmem_cache_free

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Message-ID: <20210528190732.f7lxiyl6enmtidmi@revolver>
Date:   Fri, 28 May 2021 19:07:40 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>
Subject: Re: [PATCH 23/94] radix tree test suite: Add support for
 kmem_cache_free_bulk

* Suren Baghdasaryan <surenb@...gle.com> [210528 13:55]:
> On Wed, Apr 28, 2021 at 8:36 AM Liam Howlett <liam.howlett@...cle.com> wrote:
> >
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> >  tools/testing/radix-tree/linux.c      | 9 +++++++++
> >  tools/testing/radix-tree/linux/slab.h | 1 +
> >  2 files changed, 10 insertions(+)
> >
> > diff --git a/tools/testing/radix-tree/linux.c b/tools/testing/radix-tree/linux.c
> > index 93f7de81fbe8..380bbc0a48d6 100644
> > --- a/tools/testing/radix-tree/linux.c
> > +++ b/tools/testing/radix-tree/linux.c
> > @@ -91,6 +91,15 @@ void kmem_cache_free(struct kmem_cache *cachep, void *objp)
> >         pthread_mutex_unlock(&cachep->lock);
> >  }
> >
> > +void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t size, void **list)
> > +{
> > +       if (kmalloc_verbose)
> > +               printk("Bulk free %p[0-%lu]\n", list, size - 1);
> 
> nit: Printing the address of the "list" is meaningless IMHO unless you
> output its value in kmem_cache_alloc_bulk, which you do not.

The address has been rather useful for my testing when combined with
how the list is created and the LSAN_OPTIONS="report_objects=1".  When
this information is of interest is when a test fails, so the tree will
be dumped.  Combined with the list head and the report_objects output, I
am able to deduce if there is too much in the list or too few, which
operation caused the issue, and what calculation is of interest.

Adding the alloc_bulk counterpart is not very useful because the
prediction of how many nodes are necessary is the worst-case, so the
head of the list is almost never used and the request size is already
known.  Adding that print is just noise for my use case.

> I would also suggest combining the patch introducing
> kmem_cache_alloc_bulk with this one since they seem to be
> compementary.

Yes, I agree.  I noticed this and fixed it in v2.

> 
> > +
> > +       for (int i = 0; i < size; i++)
> > +               kmem_cache_free(cachep, list[i]);
> > +}
> > +
> >  void *kmalloc(size_t size, gfp_t gfp)
> >  {
> >         void *ret;
> > diff --git a/tools/testing/radix-tree/linux/slab.h b/tools/testing/radix-tree/linux/slab.h
> > index 2958830ce4d7..53b79c15b3a2 100644
> > --- a/tools/testing/radix-tree/linux/slab.h
> > +++ b/tools/testing/radix-tree/linux/slab.h
> > @@ -24,4 +24,5 @@ struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,
> >                         unsigned int align, unsigned int flags,
> >                         void (*ctor)(void *));
> >
> > +void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t, void **);
> >  #endif         /* SLAB_H */
> > --
> > 2.30.2
> >