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Re: [Xen-devel] [PATCH] switch rangeset's lock to rwlock



On Fri, Sep 12, 2014 at 01:55:07PM +0100, Jan Beulich wrote:
> As a general library routine, it should behave as efficiently as
> possible, even if at present no significant contention is known here.
> 

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

I am comfortable with this going to Xen 4.5.

> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> With the widened use of rangesets I'd like to re-suggest this change
> which I had posted already a couple of years back.
> 
> --- a/xen/common/rangeset.c
> +++ b/xen/common/rangeset.c
> @@ -28,7 +28,7 @@ struct rangeset {
>  
>      /* Number of ranges that can be allocated */
>      long             nr_ranges;
> -    spinlock_t       lock;
> +    rwlock_t         lock;
>  
>      /* Pretty-printing name. */
>      char             name[32];
> @@ -120,7 +120,7 @@ int rangeset_add_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    write_lock(&r->lock);
>  
>      x = find_range(r, s);
>      y = find_range(r, e);
> @@ -176,7 +176,7 @@ int rangeset_add_range(
>      }
>  
>   out:
> -    spin_unlock(&r->lock);
> +    write_unlock(&r->lock);
>      return rc;
>  }
>  
> @@ -188,7 +188,7 @@ int rangeset_remove_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    write_lock(&r->lock);
>  
>      x = find_range(r, s);
>      y = find_range(r, e);
> @@ -244,7 +244,7 @@ int rangeset_remove_range(
>      }
>  
>   out:
> -    spin_unlock(&r->lock);
> +    write_unlock(&r->lock);
>      return rc;
>  }
>  
> @@ -256,10 +256,10 @@ int rangeset_contains_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>      x = find_range(r, s);
>      contains = (x && (x->e >= e));
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  
>      return contains;
>  }
> @@ -272,10 +272,10 @@ int rangeset_overlaps_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>      x = find_range(r, e);
>      overlaps = (x && (s <= x->e));
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  
>      return overlaps;
>  }
> @@ -287,13 +287,13 @@ int rangeset_report_ranges(
>      struct range *x;
>      int rc = 0;
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>  
>      for ( x = find_range(r, s); x && (x->s <= e) && !rc; x = next_range(r, 
> x) )
>          if ( x->e >= s )
>              rc = cb(max(x->s, s), min(x->e, e), ctxt);
>  
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  
>      return rc;
>  }
> @@ -331,7 +331,7 @@ struct rangeset *rangeset_new(
>      if ( r == NULL )
>          return NULL;
>  
> -    spin_lock_init(&r->lock);
> +    rwlock_init(&r->lock);
>      INIT_LIST_HEAD(&r->range_list);
>      r->nr_ranges = -1;
>  
> @@ -414,21 +414,21 @@ void rangeset_swap(struct rangeset *a, s
>  
>      if ( a < b )
>      {
> -        spin_lock(&a->lock);
> -        spin_lock(&b->lock);
> +        write_lock(&a->lock);
> +        write_lock(&b->lock);
>      }
>      else
>      {
> -        spin_lock(&b->lock);
> -        spin_lock(&a->lock);
> +        write_lock(&b->lock);
> +        write_lock(&a->lock);
>      }
>  
>      list_splice_init(&a->range_list, &tmp);
>      list_splice_init(&b->range_list, &a->range_list);
>      list_splice(&tmp, &b->range_list);
>  
> -    spin_unlock(&a->lock);
> -    spin_unlock(&b->lock);
> +    write_unlock(&a->lock);
> +    write_unlock(&b->lock);
>  }
>  
>  /*****************************
> @@ -446,7 +446,7 @@ void rangeset_printk(
>      int nr_printed = 0;
>      struct range *x;
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>  
>      printk("%-10s {", r->name);
>  
> @@ -465,7 +465,7 @@ void rangeset_printk(
>  
>      printk(" }");
>  
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  }
>  
>  void rangeset_domain_printk(
> 
> 
> 

> switch rangeset's lock to rwlock
> 
> As a general library routine, it should behave as efficiently as
> possible, even if at present no significant contention is known here.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> With the widened use of rangesets I'd like to re-suggest this change
> which I had posted already a couple of years back.
> 
> --- a/xen/common/rangeset.c
> +++ b/xen/common/rangeset.c
> @@ -28,7 +28,7 @@ struct rangeset {
>  
>      /* Number of ranges that can be allocated */
>      long             nr_ranges;
> -    spinlock_t       lock;
> +    rwlock_t         lock;
>  
>      /* Pretty-printing name. */
>      char             name[32];
> @@ -120,7 +120,7 @@ int rangeset_add_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    write_lock(&r->lock);
>  
>      x = find_range(r, s);
>      y = find_range(r, e);
> @@ -176,7 +176,7 @@ int rangeset_add_range(
>      }
>  
>   out:
> -    spin_unlock(&r->lock);
> +    write_unlock(&r->lock);
>      return rc;
>  }
>  
> @@ -188,7 +188,7 @@ int rangeset_remove_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    write_lock(&r->lock);
>  
>      x = find_range(r, s);
>      y = find_range(r, e);
> @@ -244,7 +244,7 @@ int rangeset_remove_range(
>      }
>  
>   out:
> -    spin_unlock(&r->lock);
> +    write_unlock(&r->lock);
>      return rc;
>  }
>  
> @@ -256,10 +256,10 @@ int rangeset_contains_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>      x = find_range(r, s);
>      contains = (x && (x->e >= e));
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  
>      return contains;
>  }
> @@ -272,10 +272,10 @@ int rangeset_overlaps_range(
>  
>      ASSERT(s <= e);
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>      x = find_range(r, e);
>      overlaps = (x && (s <= x->e));
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  
>      return overlaps;
>  }
> @@ -287,13 +287,13 @@ int rangeset_report_ranges(
>      struct range *x;
>      int rc = 0;
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>  
>      for ( x = find_range(r, s); x && (x->s <= e) && !rc; x = next_range(r, 
> x) )
>          if ( x->e >= s )
>              rc = cb(max(x->s, s), min(x->e, e), ctxt);
>  
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  
>      return rc;
>  }
> @@ -331,7 +331,7 @@ struct rangeset *rangeset_new(
>      if ( r == NULL )
>          return NULL;
>  
> -    spin_lock_init(&r->lock);
> +    rwlock_init(&r->lock);
>      INIT_LIST_HEAD(&r->range_list);
>      r->nr_ranges = -1;
>  
> @@ -414,21 +414,21 @@ void rangeset_swap(struct rangeset *a, s
>  
>      if ( a < b )
>      {
> -        spin_lock(&a->lock);
> -        spin_lock(&b->lock);
> +        write_lock(&a->lock);
> +        write_lock(&b->lock);
>      }
>      else
>      {
> -        spin_lock(&b->lock);
> -        spin_lock(&a->lock);
> +        write_lock(&b->lock);
> +        write_lock(&a->lock);
>      }
>  
>      list_splice_init(&a->range_list, &tmp);
>      list_splice_init(&b->range_list, &a->range_list);
>      list_splice(&tmp, &b->range_list);
>  
> -    spin_unlock(&a->lock);
> -    spin_unlock(&b->lock);
> +    write_unlock(&a->lock);
> +    write_unlock(&b->lock);
>  }
>  
>  /*****************************
> @@ -446,7 +446,7 @@ void rangeset_printk(
>      int nr_printed = 0;
>      struct range *x;
>  
> -    spin_lock(&r->lock);
> +    read_lock(&r->lock);
>  
>      printk("%-10s {", r->name);
>  
> @@ -465,7 +465,7 @@ void rangeset_printk(
>  
>      printk(" }");
>  
> -    spin_unlock(&r->lock);
> +    read_unlock(&r->lock);
>  }
>  
>  void rangeset_domain_printk(

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> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel


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