Re: [Xen-devel] [PATCH 13/16] tmem: cleanup: __tmem_alloc_page: drop unneed parameters

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Nov 26, 2013 at 04:41:42PM +0800, Bob Liu wrote:
> 
> On 11/23/2013 02:17 AM, Konrad Rzeszutek Wilk wrote:
> > On Wed, Nov 20, 2013 at 04:46:22PM +0800, Bob Liu wrote:
> >> The two parameters of __tmem_alloc_page() can be reduced.
> > 
> > That is dangerous. The last one (no_heap) was added to guard
> > against recursion. Check how tmem_alloc_page_thispool calls
> > alloc_domheap_pages, whcih calls alloc_heap_pages which
> > can call tmem_relinquish_pages, which can .. well, you will
> > get the idea.

And I think that is not an issue anymore.
> > 
> >> tmem_called_from_tmem() was also dropped by this patch.
> >>
> >> Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
> >> ---
> >>  xen/common/tmem.c          |   13 +++++--------
> >>  xen/include/xen/tmem_xen.h |   11 +++++------
> >>  2 files changed, 10 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/xen/common/tmem.c b/xen/common/tmem.c
> >> index ee61899..bf0fa1b 100644
> >> --- a/xen/common/tmem.c
> >> +++ b/xen/common/tmem.c
> >> @@ -245,7 +245,7 @@ static struct page_info *tmem_alloc_page(struct 
> >> tmem_pool *pool)
> >>      if ( pool != NULL && is_persistent(pool) )
> >>          pfp = __tmem_alloc_page_thispool(pool->client->domain);
> >>      else
> >> -        pfp = __tmem_alloc_page(pool,0);
> >> +        pfp = __tmem_alloc_page();
> >>      return pfp;
> >>  }
> >>  
> >> @@ -263,9 +263,8 @@ static noinline void *tmem_mempool_page_get(unsigned 
> >> long size)
> >>      struct page_info *pi;
> >>  
> >>      ASSERT(size == PAGE_SIZE);
> >> -    if ( (pi = __tmem_alloc_page(NULL,0)) == NULL )
> >> +    if ( (pi = __tmem_alloc_page()) == NULL )
> >>          return NULL;
> >> -    ASSERT(IS_VALID_PAGE(pi));
> >>      return page_to_virt(pi);
> >>  }
> >>  
> >> @@ -2450,7 +2449,6 @@ void tmem_freeze_all(unsigned char key)
> >>  void *tmem_relinquish_pages(unsigned int order, unsigned int memflags)
> >>  {
> >>      struct page_info *pfp;
> >> -    unsigned long evicts_per_relinq = 0;
> >>      int max_evictions = 10;
> >>  
> >>      if (!tmem_enabled() || !tmem_freeable_pages())
> >> @@ -2464,14 +2462,13 @@ void *tmem_relinquish_pages(unsigned int order, 
> >> unsigned int memflags)
> >>          return NULL;
> >>      }
> >>  
> >> -    if ( tmem_called_from_tmem(memflags) )
> >> +    if ( memflags & MEMF_tmem )
> >>          read_lock(&tmem_rwlock);
> >>  
> >> -    while ( (pfp = __tmem_alloc_page(NULL,1)) == NULL )
> >> +    while ( (pfp = tmem_page_list_get()) == NULL )
> > 
> > No no. That could lead to bad recursion. You need to pass '1' somehow.
> > 
> 
> I don't think so.
> If pass '1' to __tmem_alloc_page(), __tmem_alloc_page() only call
> tmem_page_list_get() and return.
> It's no difference, so an extra parameter is unneeded.
 
Right! Thanks for spotting that. I read that new change as:
 +    while ( (pfp = __tmem_alloc_page()) == NULL )

!
> 
> > 
> >>      {
> >>          if ( (max_evictions-- <= 0) || !tmem_evict())
> >>              break;
> >> -        evicts_per_relinq++;
> > 
> > 
> > ? Should this be a seperate patch?
> > 
> >>      }
> >>      if ( pfp != NULL )
> >>      {
> >> @@ -2479,7 +2476,7 @@ void *tmem_relinquish_pages(unsigned int order, 
> >> unsigned int memflags)
> >>              scrub_one_page(pfp);
> >>      }
> >>  
> >> -    if ( tmem_called_from_tmem(memflags) )
> >> +    if ( memflags & MEMF_tmem )
> > 
> > Perhaps a comment too? /* Called recursively from within tmem. */
> > 
> >>          read_unlock(&tmem_rwlock);
> >>  
> >>      return pfp;
> >> diff --git a/xen/include/xen/tmem_xen.h b/xen/include/xen/tmem_xen.h
> >> index 7468c28..c4b9f5a 100644
> >> --- a/xen/include/xen/tmem_xen.h
> >> +++ b/xen/include/xen/tmem_xen.h
> >> @@ -144,15 +144,16 @@ static inline void __tmem_free_page_thispool(struct 
> >> page_info *pi)
> >>  /*
> >>   * Memory allocation for ephemeral (non-persistent) data
> >>   */
> >> -static inline struct page_info *__tmem_alloc_page(void *pool, int no_heap)
> >> +static inline struct page_info *__tmem_alloc_page(void)

> >>  {
> >>      struct page_info *pi = tmem_page_list_get();
> >>  
> >> -    if ( pi == NULL && !no_heap )
> >> +    if ( pi == NULL)
> >>          pi = alloc_domheap_pages(0,0,MEMF_tmem);
> >> -    ASSERT((pi == NULL) || IS_VALID_PAGE(pi));
> >> -    if ( pi != NULL && !no_heap )
> >> +
> >> +    if ( pi )
> >>          atomic_inc(&freeable_page_count);
> >> +    ASSERT((pi == NULL) || IS_VALID_PAGE(pi));
> >>      return pi;
> >>  }
> >>  
> 
> See __tmem_alloc_page() implementation here.

<nods>
> 
> -- 
> Regards,
> -Bob

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel