[Mesa-dev] [PATCH 7/8] gallium/util: add a linear allocator for reducing malloc overhead

[Bas Nieuwenhuizen]

On Fri, Jan 18, 2019 at 5:44 PM Marek Olšák <maraeo at gmail.com> wrote:
>
> From: Marek Olšák <marek.olsak at amd.com>
>
> ---
>  src/gallium/auxiliary/Makefile.sources      |  1 +
>  src/gallium/auxiliary/meson.build           |  1 +
>  src/gallium/auxiliary/util/u_cpu_suballoc.h | 90 +++++++++++++++++++++
>  3 files changed, 92 insertions(+)
>  create mode 100644 src/gallium/auxiliary/util/u_cpu_suballoc.h
>
> diff --git a/src/gallium/auxiliary/Makefile.sources b/src/gallium/auxiliary/Makefile.sources
> index 50e88088ff8..b26415858f6 100644
> --- a/src/gallium/auxiliary/Makefile.sources
> +++ b/src/gallium/auxiliary/Makefile.sources
> @@ -211,20 +211,21 @@ C_SOURCES := \
>         util/u_bitmask.c \
>         util/u_bitmask.h \
>         util/u_blend.h \
>         util/u_blit.c \
>         util/u_blit.h \
>         util/u_blitter.c \
>         util/u_blitter.h \
>         util/u_box.h \
>         util/u_cache.c \
>         util/u_cache.h \
> +       util/u_cpu_suballoc.h \
>         util/u_debug_gallium.h \
>         util/u_debug_gallium.c \
>         util/u_debug_describe.c \
>         util/u_debug_describe.h \
>         util/u_debug_flush.c \
>         util/u_debug_flush.h \
>         util/u_debug_image.c \
>         util/u_debug_image.h \
>         util/u_debug_memory.c \
>         util/u_debug_refcnt.c \
> diff --git a/src/gallium/auxiliary/meson.build b/src/gallium/auxiliary/meson.build
> index 57f7e69050f..7e1e4732421 100644
> --- a/src/gallium/auxiliary/meson.build
> +++ b/src/gallium/auxiliary/meson.build
> @@ -231,20 +231,21 @@ files_libgallium = files(
>    'util/u_bitmask.c',
>    'util/u_bitmask.h',
>    'util/u_blend.h',
>    'util/u_blit.c',
>    'util/u_blit.h',
>    'util/u_blitter.c',
>    'util/u_blitter.h',
>    'util/u_box.h',
>    'util/u_cache.c',
>    'util/u_cache.h',
> +  'util/u_cpu_suballoc.h',
>    'util/u_debug_gallium.h',
>    'util/u_debug_gallium.c',
>    'util/u_debug_describe.c',
>    'util/u_debug_describe.h',
>    'util/u_debug_flush.c',
>    'util/u_debug_flush.h',
>    'util/u_debug_image.c',
>    'util/u_debug_image.h',
>    'util/u_debug_memory.c',
>    'util/u_debug_refcnt.c',
> diff --git a/src/gallium/auxiliary/util/u_cpu_suballoc.h b/src/gallium/auxiliary/util/u_cpu_suballoc.h
> new file mode 100644
> index 00000000000..2373c1f7c70
> --- /dev/null
> +++ b/src/gallium/auxiliary/util/u_cpu_suballoc.h
> @@ -0,0 +1,90 @@
> +/**************************************************************************
> + *
> + * Copyright 2019 Advanced Micro Devices, Inc.
> + * All Rights Reserved.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the
> + * "Software"), to deal in the Software without restriction, including
> + * without limitation the rights to use, copy, modify, merge, publish,
> + * distribute, sub license, and/or sell copies of the Software, and to
> + * permit persons to whom the Software is furnished to do so, subject to
> + * the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the
> + * next paragraph) shall be included in all copies or substantial portions
> + * of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
> + * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
> + * IN NO EVENT SHALL AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR
> + * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
> + * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
> + * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
> + *
> + **************************************************************************/
> +
> +/* A simple utility for suballocating out of malloc_aligned. */
> +
> +#ifndef U_CPU_SUBALLOC_H
> +#define U_CPU_SUBALLOC_H
> +
> +#include <stdint.h>
> +#include "util/os_memory.h"
> +
> +struct u_cpu_suballoc {
> +   unsigned default_size;  /* Default size of the buffer, in bytes. */
> +   unsigned current_size;  /* Current size of the buffer, in bytes. */
> +   unsigned alignment;     /* malloc alignment. */
> +   unsigned offset;        /* Offset pointing to the first unused byte. */
> +   uint8_t *buffer;        /* Pointer to the CPU buffer. */
> +};
> +
> +
> +static inline void
> +u_cpu_suballoc_init(struct u_cpu_suballoc *alloc, unsigned default_size,
> +                   unsigned alignment)
> +{
> +   memset(alloc, 0, sizeof(*alloc));
> +   alloc->default_size = default_size;
> +   alloc->alignment = alignment;
> +}
> +
> +
> +static inline void
> +u_cpu_suballoc_deinit(struct u_cpu_suballoc *alloc)
> +{
> +   os_free_aligned(alloc->buffer);
> +   alloc->buffer = NULL;
> +}
> +
> +
> +static inline void *
> +u_cpu_suballoc(struct u_cpu_suballoc *alloc, unsigned size, unsigned alignment)
> +{
> +   unsigned offset = align(alloc->offset, alignment);
> +
> +   /* Make sure we have enough space in the buffer for the sub-allocation. */
> +   if (unlikely(!alloc->buffer || offset + size > alloc->current_size)) {
> +      os_free_aligned(alloc->buffer);

So, if we can free the memory during a suballocation, how do we make
sure that the previous allocations are valid? If they don't have to
stay valid, why use a linear allocator at all?
> +
> +      alloc->current_size = MAX2(alloc->default_size, size);
> +      alloc->offset = 0;
> +      alloc->buffer = (uint8_t*)os_malloc_aligned(alloc->current_size,
> +                                                  alloc->alignment);
> +
> +      if (unlikely(!alloc->buffer))
> +         return NULL;
> +
> +      offset = 0;
> +   }
> +
> +   assert(offset + size <= alloc->current_size);
> +
> +   void *ptr = alloc->buffer + offset;
> +   alloc->offset = offset + size;
> +   return ptr;
> +}
> +
> +#endif
> --
> 2.17.1
>
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