Re: [Xen-devel] [PATCH v2 2/3] xen: remove tmem from hypervisor

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.11.18 at 14:58, <wei.liu2@xxxxxxxxxx> wrote:
> @@ -250,7 +249,7 @@ static void populate_physmap(struct memop_args *a)
>  
>                  if ( unlikely(!page) )
>                  {
> -                    if ( !tmem_enabled() || a->extent_order )
> +                    if ( a->extent_order )
>                          gdprintk(XENLOG_INFO,
>                                   "Could not allocate order=%u extent: id=%d 
> memflags=%#x (%u of %u)\n",
>                                   a->extent_order, d->domain_id, a->memflags,

From an abstract pov without tmem tmem_enabled() should return constant
"false". Which seems to mean that the if() should go away rather than its
condition getting changed.

> @@ -949,22 +935,6 @@ static struct page_info *alloc_heap_pages(
>          return NULL;
>      }
>  
> -    /*
> -     * TMEM: When available memory is scarce due to tmem absorbing it, allow
> -     * only mid-size allocations to avoid worst of fragmentation issues.
> -     * Others try tmem pools then fail.  This is a workaround until all
> -     * post-dom0-creation-multi-page allocations can be eliminated.
> -     */
> -    if ( ((order == 0) || (order >= 9)) &&
> -         (total_avail_pages <= midsize_alloc_zone_pages) &&
> -         tmem_freeable_pages() )
> -    {
> -        /* Try to free memory from tmem. */
> -        pg = tmem_relinquish_pages(order, memflags);
> -        spin_unlock(&heap_lock);
> -        return pg;
> -    }
> -
>      pg = get_free_buddy(zone_lo, zone_hi, order, memflags, d);
>      /* Try getting a dirty buddy if we couldn't get a clean one. */
>      if ( !pg && !(memflags & MEMF_no_scrub) )
> @@ -1444,10 +1414,6 @@ static void free_heap_pages(
>      else
>          pg->u.free.first_dirty = INVALID_DIRTY_IDX;
>  
> -    if ( tmem_enabled() )
> -        midsize_alloc_zone_pages = max(
> -            midsize_alloc_zone_pages, total_avail_pages / 
> MIDSIZE_ALLOC_FRAC);

Seeing these two hunks I think midsize_alloc_zone_pages and
MIDSIZE_ALLOC_FRAC want to go away altogether.

> --- a/xen/include/xen/mm.h
> +++ b/xen/include/xen/mm.h
> @@ -248,8 +248,10 @@ struct npfec {
>  #define  MEMF_no_refcount (1U<<_MEMF_no_refcount)
>  #define _MEMF_populate_on_demand 1
>  #define  MEMF_populate_on_demand (1U<<_MEMF_populate_on_demand)
> +#if 0
>  #define _MEMF_tmem        2
>  #define  MEMF_tmem        (1U<<_MEMF_tmem)
> +#endif

Why "#if 0" rather than removing the two lines?

With these suitably taken care of feel free to add
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



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