On Sat, Oct 15, 2022 at 10:15:12PM +0800, Zhang Boyang wrote:
> Previously, there are two problems of the handling of adding new
Please drop "Previously". It is not needed...
> regions. First, it doesn't take region management cost into account.
> Adding a memory area of `x` bytes will result in a heap region of less
> than `x` bytes avaliable. Thus, the new region might not adequate for
> current allocation request. Second, it doesn't pre-allocate a big region
> for small allocations, so it might be slow for many small allocations.
>
> This patch introduces GRUB_MM_MAX_COST to address the cost of region
> management. The value of this constant should make
> `grub_mm_init_region (addr, size + GRUB_MM_MAX_COST)` initialize a
> region of at least `size` free bytes available. The size of heap growth
> is now adjusted according this value before calling
> grub_mm_add_region_fn ().
This should be separate patch...
> This patch also introduces GRUB_MM_HEAP_GROW to address the minimal heap
> growth granularity. When a small allocation encounters heap space
> exhaustion, the size of heap growth is now expended to this value, and a
> new region of bigger size will be added. Thus subsequent allocations can
> use the remaining space of that new region.
... and this should be the second one, to be precise third patch in the
series...
> Signed-off-by: Zhang Boyang <zhangboyang...@gmail.com>
> ---
> grub-core/kern/mm.c | 18 +++++++++++++++---
> include/grub/mm_private.h | 12 ++++++++++++
> 2 files changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c
> index ae2279133..fe630f061 100644
> --- a/grub-core/kern/mm.c
> +++ b/grub-core/kern/mm.c
> @@ -410,7 +410,9 @@ grub_memalign (grub_size_t align, grub_size_t size)
> {
> grub_mm_region_t r;
> grub_size_t n = ((size + GRUB_MM_ALIGN - 1) >> GRUB_MM_ALIGN_LOG2) + 1;
> + grub_size_t guarantee;
> int count = 0;
> + grub_size_t grow;
>
> if (!grub_mm_base)
> goto fail;
> @@ -418,10 +420,13 @@ grub_memalign (grub_size_t align, grub_size_t size)
> if (size > ~(grub_size_t) align)
> goto fail;
>
> + /* Allocation can always success if max continuous free chunk >= guarantee
> */
> + guarantee = size + align;
> +
> /* We currently assume at least a 32-bit grub_size_t,
> so limiting allocations to <adress space size> - 1MiB
> in name of sanity is beneficial. */
> - if ((size + align) > ~(grub_size_t) 0x100000)
> + if (guarantee > ~(grub_size_t) 0x100000)
> goto fail;
>
> align = (align >> GRUB_MM_ALIGN_LOG2);
> @@ -443,11 +448,18 @@ grub_memalign (grub_size_t align, grub_size_t size)
> switch (count)
> {
> case 0:
> + /* Calculate optimal size of heap growth. */
> + grow = grub_max(guarantee, GRUB_MM_HEAP_GROW);
Missing space before "(".
> +
> + /* Adjust heap growth to address the cost of region management. */
> + if (grub_add(grow, GRUB_MM_MAX_COST, &grow))
Ditto...
> + goto fail;
> +
> /* Request additional pages, contiguous */
> count++;
>
> if (grub_mm_add_region_fn != NULL &&
> - grub_mm_add_region_fn (size, GRUB_MM_ADD_REGION_CONSECUTIVE) ==
> GRUB_ERR_NONE)
> + grub_mm_add_region_fn (grow, GRUB_MM_ADD_REGION_CONSECUTIVE) ==
> GRUB_ERR_NONE)
> goto again;
>
> /* fallthrough */
> @@ -462,7 +474,7 @@ grub_memalign (grub_size_t align, grub_size_t size)
> * Try again even if this fails, in case it was able to partially
> * satisfy the request
> */
> - grub_mm_add_region_fn (size, GRUB_MM_ADD_REGION_NONE);
> + grub_mm_add_region_fn (grow, GRUB_MM_ADD_REGION_NONE);
> goto again;
> }
>
> diff --git a/include/grub/mm_private.h b/include/grub/mm_private.h
> index 96c2d816b..a01ba2507 100644
> --- a/include/grub/mm_private.h
> +++ b/include/grub/mm_private.h
> @@ -95,6 +95,18 @@ typedef struct grub_mm_region
> }
> *grub_mm_region_t;
>
> +/*
> + * Set an upper bound of management cost of each region,
> + * with sizeof(struct grub_mm_region), sizeof(struct grub_mm_header) and
> + * any possible alignment or padding taken into account.
OK...
> + * The value should make `grub_mm_init_region (addr, size +
> GRUB_MM_MAX_COST)`
> + * initialize a region of at least `size` free bytes available.
> + */
> +#define GRUB_MM_MAX_COST 0x1000
... but why do not you use sizeof() here then?
> +
> +/* Minimal heap growth granularity, when existing heap space is exhausted. */
> +#define GRUB_MM_HEAP_GROW 0x100000
It would be nice if you shortly explain in the comment before why you
come up with this value.
Daniel
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