linux-kernel - Re: [PATCH] SLOB allocator imcompatible SLAB

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Message-ID: <m2ejk05y7c.wl%ysato@users.sourceforge.jp>
Date:	Mon, 25 Jun 2007 15:45:43 +0900
From:	Yoshinori Sato <ysato@...rs.sourceforge.jp>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] SLOB allocator imcompatible SLAB

At Fri, 22 Jun 2007 09:56:35 -0500,
Matt Mackall wrote:
> 
> On Fri, Jun 22, 2007 at 05:08:07PM +0900, Yoshinori Sato wrote:
> > Because the page which SLOB allocator got does not have PG_slab,
> 
> This is for a NOMMU system?

Yes.
 
> You're using an old kernel with an old version of SLOB. SLOB in newer
> kernels actually sets per-page flags. Nick, can you see any reason not
> to s/PG_active/PG_slab/ in the current code?

in mm/nommu.c
   109  unsigned int kobjsize(const void *objp)
   110  {
    :
   116          if (PageSlab(page))
   117                  return ksize(objp);
    :
   122          return (PAGE_SIZE << page->index);
   123  }

PG_slab is verified here.


> > Signed-off-by: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> > 
> > diff --git a/mm/slob.c b/mm/slob.c
> > index 71976c5..d10bcda 100644
> > --- a/mm/slob.c
> > +++ b/mm/slob.c
> > @@ -73,6 +73,21 @@ static DEFINE_SPINLOCK(block_lock);
> >  static void slob_free(void *b, int size);
> >  static void slob_timer_cbk(void);
> >  
> > +static inline void set_slabflags(const void *ptr, int order)
> > +{
> > +	int i;
> > +	struct page *page = virt_to_page(ptr);
> > +	for (i = 0; i < (1 << order); i++)
> > +		__SetPageSlab(page++);
> > +}
> > +
> > +static inline void clear_slabflags(const void *ptr, int order)
> > +{
> > +	int i;
> > +	struct page *page = virt_to_page(ptr);
> > +	for (i = 0; i < (1 << order); i++)
> > +		__ClearPageSlab(page++);
> > +}
> >  
> >  static void *slob_alloc(size_t size, gfp_t gfp, int align)
> >  {
> > @@ -180,6 +195,7 @@ void *__kmalloc(size_t size, gfp_t gfp)
> >  	bb->pages = (void *)__get_free_pages(gfp, bb->order);
> >  
> >  	if (bb->pages) {
> > +		set_slabflags(bb->pages, bb->order);
> >  		spin_lock_irqsave(&block_lock, flags);
> >  		bb->next = bigblocks;
> >  		bigblocks = bb;
> > @@ -240,6 +256,7 @@ void kfree(const void *block)
> >  			if (bb->pages == block) {
> >  				*last = bb->next;
> >  				spin_unlock_irqrestore(&block_lock, flags);
> > +				clear_slabflags(block, bb->order);
> >  				free_pages((unsigned long)block, bb->order);
> >  				slob_free(bb, sizeof(bigblock_t));
> >  				return;
> > @@ -323,9 +340,11 @@ void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
> >  
> >  	if (c->size < PAGE_SIZE)
> >  		b = slob_alloc(c->size, flags, c->align);
> > -	else
> > +	else {
> >  		b = (void *)__get_free_pages(flags, get_order(c->size));
> > -
> > +		if (b)
> > +			set_slabflags(b, get_order(c->size));
> > +	}
> >  	if (c->ctor)
> >  		c->ctor(b, c, 0);
> >  
> > @@ -347,8 +366,10 @@ static void __kmem_cache_free(void *b, int size)
> >  {
> >  	if (size < PAGE_SIZE)
> >  		slob_free(b, size);
> > -	else
> > +	else {
> > +		clear_slabflags(b, get_order(size));
> >  		free_pages((unsigned long)b, get_order(size));
> > +	}
> >  }
> >  
> >  static void kmem_rcu_free(struct rcu_head *head)
> 
> -- 
> Mathematics is the supreme nostalgia of our time.
-
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