linux-kernel - Re: [PATCH 24/94] radix tree test suite: Add keme_cache_alloc

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Date:   Fri, 28 May 2021 19:28:41 +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 24/94] radix tree test suite: Add keme_cache_alloc_bulk()
 support

* Suren Baghdasaryan <surenb@...gle.com> [210528 14:17]:
> 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      | 51 +++++++++++++++++++++++++++
> >  tools/testing/radix-tree/linux/slab.h |  1 +
> >  2 files changed, 52 insertions(+)
> >
> > diff --git a/tools/testing/radix-tree/linux.c b/tools/testing/radix-tree/linux.c
> > index 380bbc0a48d6..fb19a40ebb46 100644
> > --- a/tools/testing/radix-tree/linux.c
> > +++ b/tools/testing/radix-tree/linux.c
> > @@ -99,6 +99,57 @@ void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t size, void **list)
> >         for (int i = 0; i < size; i++)
> >                 kmem_cache_free(cachep, list[i]);
> >  }
> > +int kmem_cache_alloc_bulk(struct kmem_cache *cachep, gfp_t gfp, size_t size,
> > +                         void **p)
> > +{
> > +       size_t i;
> > +
> > +       if (kmalloc_verbose)
> > +               printk("Bulk alloc %lu\n", size);
> > +
> > +       if (!(gfp & __GFP_DIRECT_RECLAIM) && cachep->non_kernel < size)
> > +               return 0;
> > +
> > +       if (!(gfp & __GFP_DIRECT_RECLAIM))
> > +               cachep->non_kernel -= size;
> > +
> > +       pthread_mutex_lock(&cachep->lock);
> > +       if (cachep->nr_objs >= size) {
> > +               struct radix_tree_node *node = cachep->objs;
> > +
> 
> I don't think the loop below is correct because "node" is not being
> changed on each iteration:
> 
> > +               for (i = 0; i < size; i++) {
> > +                       cachep->nr_objs--;
> > +                       cachep->objs = node->parent;
> 
> In the above assignment cachep->objs will be assigned the same value
> on all iterations.
> 
> > +                       p[i] = cachep->objs;
> 
> p[0] should point to the node, however here it would point to the node->parent.
> 
> > +               }
> > +               pthread_mutex_unlock(&cachep->lock);
> > +               node->parent = NULL;
> 
> here you terminated the original cachep->objs which is not even inside
> the "p" list at this point (it was skipped).

I just verified that this code wasn't hit in my current test code.  I
will test and fix this.  Good catch.

> 
> > +       } else {
> > +               pthread_mutex_unlock(&cachep->lock);
> > +               for (i = 0; i < size; i++) {
> > +                       if (cachep->align) {
> > +                               posix_memalign(&p[i], cachep->align,
> > +                                              cachep->size * size);
> > +                       } else {
> > +                               p[i] = malloc(cachep->size * size);
> > +                       }
> > +                       if (cachep->ctor)
> > +                               cachep->ctor(p[i]);
> > +                       else if (gfp & __GFP_ZERO)
> > +                               memset(p[i], 0, cachep->size);
> > +               }
> > +       }
> > +
> > +       for (i = 0; i < size; i++) {
> > +               uatomic_inc(&nr_allocated);
> > +               uatomic_inc(&nr_tallocated);
> 
> I don't see nr_tallocated even in linux-next branch. Was it introduced
> in one of the previous patches and I missed it?

It was introduced with the maple tree itself.  I will spin this off as
its own patch with the same edits as nr_allocated.

> 
> > +               if (kmalloc_verbose)
> > +                       printf("Allocating %p from slab\n", p[i]);
> > +       }
> > +
> > +       return size;
> > +}
> > +
> >
> >  void *kmalloc(size_t size, gfp_t gfp)
> >  {
> > diff --git a/tools/testing/radix-tree/linux/slab.h b/tools/testing/radix-tree/linux/slab.h
> > index 53b79c15b3a2..ba42b8cc11d0 100644
> > --- a/tools/testing/radix-tree/linux/slab.h
> > +++ b/tools/testing/radix-tree/linux/slab.h
> > @@ -25,4 +25,5 @@ struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,
> >                         void (*ctor)(void *));
> >
> >  void kmem_cache_free_bulk(struct kmem_cache *cachep, size_t, void **);
> > +int kmem_cache_alloc_bulk(struct kmem_cache *cachep, gfp_t, size_t, void **);
> >  #endif         /* SLAB_H */
> > --
> > 2.30.2