On Fri, 25 Jun 2010, Christoph Lameter wrote:
> In pcpu_alloc_info()
You mean pcpu_build_alloc_info()?
This should have a "From: Tejun Heo <tj@xxxxxxxxxx>" line, right?
> and pcpu_embed_first_chunk(), @dyn_size was
> ssize_t, -1 meant auto-size, 0 forced 0 and positive meant minimum
> size. There's no use case for forcing 0 and the upcoming early alloc
> support always requires non-zero dynamic size. Make @dyn_size always
> mean minimum dyn_size.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
>
> Index: linux-2.6/include/linux/percpu.h
> ===================================================================
> --- linux-2.6.orig/include/linux/percpu.h 2010-06-18 12:23:22.000000000 -0500
> +++ linux-2.6/include/linux/percpu.h 2010-06-18 12:24:52.000000000 -0500
> @@ -105,7 +105,7 @@ extern struct pcpu_alloc_info * __init p
> extern void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai);
>
> extern struct pcpu_alloc_info * __init pcpu_build_alloc_info(
> - size_t reserved_size, ssize_t dyn_size,
> + size_t reserved_size, size_t dyn_size,
> size_t atom_size,
> pcpu_fc_cpu_distance_fn_t cpu_distance_fn);
>
This can just be removed entirely, it's unnecessarily global.
> @@ -113,7 +113,7 @@ extern int __init pcpu_setup_first_chunk
> void *base_addr);
>
> #ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
> -extern int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
> +extern int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
> size_t atom_size,
> pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
> pcpu_fc_alloc_fn_t alloc_fn,
> Index: linux-2.6/mm/percpu.c
> ===================================================================
> --- linux-2.6.orig/mm/percpu.c 2010-06-18 11:20:35.000000000 -0500
> +++ linux-2.6/mm/percpu.c 2010-06-18 12:24:52.000000000 -0500
> @@ -988,20 +988,6 @@ phys_addr_t per_cpu_ptr_to_phys(void *ad
> return page_to_phys(pcpu_addr_to_page(addr));
> }
>
> -static inline size_t pcpu_calc_fc_sizes(size_t static_size,
> - size_t reserved_size,
> - ssize_t *dyn_sizep)
> -{
> - size_t size_sum;
> -
> - size_sum = PFN_ALIGN(static_size + reserved_size +
> - (*dyn_sizep >= 0 ? *dyn_sizep : 0));
> - if (*dyn_sizep != 0)
> - *dyn_sizep = size_sum - static_size - reserved_size;
> -
> - return size_sum;
> -}
> -
> /**
> * pcpu_alloc_alloc_info - allocate percpu allocation info
> * @nr_groups: the number of groups
> @@ -1060,7 +1046,7 @@ void __init pcpu_free_alloc_info(struct
> /**
> * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
> * @reserved_size: the size of reserved percpu area in bytes
> - * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
> + * @dyn_size: free size for dynamic allocation in bytes
It's the minimum free size, it's not necessarily the exact size due to
round-up.
> * @atom_size: allocation atom size
> * @cpu_distance_fn: callback to determine distance between cpus, optional
> *
> @@ -1079,7 +1065,7 @@ void __init pcpu_free_alloc_info(struct
> * failure, ERR_PTR value is returned.
> */
> struct pcpu_alloc_info * __init pcpu_build_alloc_info(
> - size_t reserved_size, ssize_t dyn_size,
> + size_t reserved_size, size_t dyn_size,
> size_t atom_size,
> pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
> {
> @@ -1098,13 +1084,15 @@ struct pcpu_alloc_info * __init pcpu_bui
> memset(group_map, 0, sizeof(group_map));
> memset(group_cnt, 0, sizeof(group_map));
>
> + size_sum = PFN_ALIGN(static_size + reserved_size + dyn_size);
> + dyn_size = size_sum - static_size - reserved_size;
Ok, so the only purpose of "dyn_size" is to store in the struct
pcpu_alloc_info later. Before this patch, ai->dyn_size would always be 0
if that's what was passed to pcpu_build_alloc_info(), but due to this
arithmetic it now requires that static_size + reserved_size to be pfn
aligned. Where is that enforced or do we not care?
> +
> /*
> * Determine min_unit_size, alloc_size and max_upa such that
> * alloc_size is multiple of atom_size and is the smallest
> * which can accomodate 4k aligned segments which are equal to
> * or larger than min_unit_size.
> */
> - size_sum = pcpu_calc_fc_sizes(static_size, reserved_size, &dyn_size);
> min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
>
> alloc_size = roundup(min_unit_size, atom_size);
> @@ -1508,7 +1496,7 @@ early_param("percpu_alloc", percpu_alloc
> /**
> * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
> * @reserved_size: the size of reserved percpu area in bytes
> - * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
> + * @dyn_size: minimum free size for dynamic allocation in bytes
> * @atom_size: allocation atom size
> * @cpu_distance_fn: callback to determine distance between cpus, optional
> * @alloc_fn: function to allocate percpu page
> @@ -1529,10 +1517,7 @@ early_param("percpu_alloc", percpu_alloc
> * vmalloc space is not orders of magnitude larger than distances
> * between node memory addresses (ie. 32bit NUMA machines).
> *
> - * When @dyn_size is positive, dynamic area might be larger than
> - * specified to fill page alignment. When @dyn_size is auto,
> - * @dyn_size is just big enough to fill page alignment after static
> - * and reserved areas.
> + * @dyn_size specifies the minimum dynamic area size.
> *
> * If the needed size is smaller than the minimum or specified unit
> * size, the leftover is returned using @free_fn.
> @@ -1540,7 +1525,7 @@ early_param("percpu_alloc", percpu_alloc
> * RETURNS:
> * 0 on success, -errno on failure.
> */
> -int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
> +int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
> size_t atom_size,
> pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
> pcpu_fc_alloc_fn_t alloc_fn,
> @@ -1671,7 +1656,7 @@ int __init pcpu_page_first_chunk(size_t
>
> snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
>
> - ai = pcpu_build_alloc_info(reserved_size, -1, PAGE_SIZE, NULL);
> + ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
> if (IS_ERR(ai))
> return PTR_ERR(ai);
> BUG_ON(ai->nr_groups != 1);
>
>
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