[Mesa-dev] [PATCH 7/8] gallium/util: add a linear allocator for reducing malloc overhead
Bas Nieuwenhuizen
bas at basnieuwenhuizen.nl
Sat Jan 19 01:21:06 UTC 2019
On Sat, Jan 19, 2019 at 2:10 AM Marek Olšák <maraeo at gmail.com> wrote:
>
> On Fri, Jan 18, 2019 at 6:08 PM Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl> wrote:
>>
>> 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?
>
>
> The assumption is that previously allocated memory won't be accessed after the next call to u_cpu_suballoc. Yeah it's pretty fragile.
What is the point then of having this as suballocator? If we just want
to cache a memory allocation, why not keep offset at 0 (or rather
remove it completely)?
>
> Marek
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