| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CA+M3ks7i-px=7LeiHw=3ZS3UEEpJFAa4A5yJFQDqut+6Dxv_gg@mail.gmail.com>
Date: Thu, 13 Sep 2012 14:14:52 +0200
From: Benjamin Gaignard <benjamin.gaignard@...aro.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Huang Ying <ying.huang@...el.com>, linux-kernel@...r.kernel.org,
Benjamin Gaignard <benjamin.gaignard@...ricsson.com>
Subject: Re: [PATCH] genalloc: make possible to use a custom allocation algorithm
>From b78b2fea3899c5170b780f5ff138490ac6cf4cb7 Mon Sep 17 00:00:00 2001
From: Benjamin Gaignard <benjamin.gaignard@...ricsson.com>
Date: Thu, 13 Sep 2012 11:29:03 +0200
Subject: [PATCH] genalloc: make possible to use a custom allocation algorithm
This patch allow to use another algorithm than the default first-fit one.
For example a custom algorithm could be used to manage alignment requirements.
As I can't predict all the possible requirements/needs for all allocation
uses cases, I add a "free" field 'void *data' to pass any needed information
to the allocation function. For example 'data' could be used to handle
a structure
where you store the alignment, the expected memory bank, the requester
device, or any information that could influence the allocation algorithm.
An usage example may look like this:
struct my_pool_constraints {
int align;
int bank;
...
};
unsigned long my_custom_algo(unsigned long *map, unsigned long size,
unsigned long start, unsigned int nr, void *data)
{
struct my_pool_constraints *constraints = data;
...
deal with allocation contraints
...
return the index in bitmap where perform the allocation
}
void create_my_pool()
{
struct my_pool_constraints c;
struct gen_pool *pool = gen_pool_create(...);
gen_pool_add(pool, ...);
gen_pool_set_algo(pool, my_custom_algo, &c);
}
Add of best-fit algorithm function:
most of the time best-fit is slower then first-fit but memory fragmentation
is lower. The random buffer allocation/free tests don't show any arithmetic
relation between the allocation time and fragmentation but the
best-fit algorithm
is sometime able to perform the allocation when the first-fit can't.
This new algorithm help to remove static allocations on ESRAM, a small but
fast on-chip RAM of few KB, used for high-performance uses cases like DMA
linked lists, graphic accelerators, encoders/decoders. On the Ux500
(in the ARM tree) we have define 5 ESRAM banks of 128 KB each and use of
static allocations becomes unmaintainable:
cd arch/arm/mach-ux500 && grep -r ESRAM .
./include/mach/db8500-regs.h:/* Base address and bank offsets for ESRAM */
./include/mach/db8500-regs.h:#define U8500_ESRAM_BASE 0x40000000
./include/mach/db8500-regs.h:#define U8500_ESRAM_BANK_SIZE 0x00020000
./include/mach/db8500-regs.h:#define U8500_ESRAM_BANK0 U8500_ESRAM_BASE
./include/mach/db8500-regs.h:#define
U8500_ESRAM_BANK1 (U8500_ESRAM_BASE + U8500_ESRAM_BANK_SIZE)
./include/mach/db8500-regs.h:#define
U8500_ESRAM_BANK2 (U8500_ESRAM_BANK1 + U8500_ESRAM_BANK_SIZE)
./include/mach/db8500-regs.h:#define
U8500_ESRAM_BANK3 (U8500_ESRAM_BANK2 + U8500_ESRAM_BANK_SIZE)
./include/mach/db8500-regs.h:#define
U8500_ESRAM_BANK4 (U8500_ESRAM_BANK3 + U8500_ESRAM_BANK_SIZE)
./include/mach/db8500-regs.h:#define U8500_ESRAM_DMA_LCPA_OFFSET 0x10000
./include/mach/db8500-regs.h:#define U8500_DMA_LCPA_BASE
(U8500_ESRAM_BANK0 + U8500_ESRAM_DMA_LCPA_OFFSET)
./include/mach/db8500-regs.h:#define U8500_DMA_LCLA_BASE U8500_ESRAM_BANK4
I want to use genalloc to do dynamic allocations but I need to be able to
fine tune the allocation algorithm. I my case best-fit algorithm give
better results than first-fit, but it will not be true for every use case.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...ricsson.com>
---
include/linux/genalloc.h | 27 ++++++++++++++
lib/genalloc.c | 88 +++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 111 insertions(+), 4 deletions(-)
diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index 5e98eeb..dd7c569 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h
@@ -29,6 +29,20 @@
#ifndef __GENALLOC_H__
#define __GENALLOC_H__
+/**
+ * Allocation callback function type definition
+ * @map: Pointer to bitmap
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @data: optional additional data used by @genpool_algo_t
+ */
+typedef unsigned long (*genpool_algo_t)(unsigned long *map,
+ unsigned long size,
+ unsigned long start,
+ unsigned int nr,
+ void *data);
+
/*
* General purpose special memory pool descriptor.
*/
@@ -36,6 +50,9 @@ struct gen_pool {
spinlock_t lock;
struct list_head chunks; /* list of chunks in this pool */
int min_alloc_order; /* minimum allocation order */
+
+ genpool_algo_t algo; /* allocation function */
+ void *data;
};
/*
@@ -78,4 +95,14 @@ extern void gen_pool_for_each_chunk(struct gen_pool *,
void (*)(struct gen_pool *, struct gen_pool_chunk *, void *), void *);
extern size_t gen_pool_avail(struct gen_pool *);
extern size_t gen_pool_size(struct gen_pool *);
+
+extern void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo,
+ void *data);
+
+extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
+ unsigned long start, unsigned int nr, void *data);
+
+extern unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
+ unsigned long start, unsigned int nr, void *data);
+
#endif /* __GENALLOC_H__ */
diff --git a/lib/genalloc.c b/lib/genalloc.c
index 6bc04aa..ca208a9 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -152,6 +152,8 @@ struct gen_pool *gen_pool_create(int
min_alloc_order, int nid)
spin_lock_init(&pool->lock);
INIT_LIST_HEAD(&pool->chunks);
pool->min_alloc_order = min_alloc_order;
+ pool->algo = gen_pool_first_fit;
+ pool->data = NULL;
}
return pool;
}
@@ -255,8 +257,9 @@ EXPORT_SYMBOL(gen_pool_destroy);
* @size: number of bytes to allocate from the pool
*
* Allocate the requested number of bytes from the specified pool.
- * Uses a first-fit algorithm. Can not be used in NMI handler on
- * architectures without NMI-safe cmpxchg implementation.
+ * Uses the pool allocation function (with first-fit algorithm by default).
+ * Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
*/
unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
{
@@ -280,8 +283,8 @@ unsigned long gen_pool_alloc(struct gen_pool
*pool, size_t size)
end_bit = (chunk->end_addr - chunk->start_addr) >> order;
retry:
- start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit,
- start_bit, nbits, 0);
+ start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
+ pool->data);
if (start_bit >= end_bit)
continue;
remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
@@ -400,3 +403,80 @@ size_t gen_pool_size(struct gen_pool *pool)
return size;
}
EXPORT_SYMBOL_GPL(gen_pool_size);
+
+/**
+ * gen_pool_set_algo - set the allocation algorithm
+ * @pool: pool to change allocation algorithm
+ * @algo: custom algorithm function
+ * @data: additional data used by @algo
+ *
+ * Call @algo for each memory allocation in the pool.
+ * If @algo is NULL use gen_pool_first_fit as default
+ * memory allocation function.
+ */
+void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo, void *data)
+{
+ rcu_read_lock();
+
+ pool->algo = algo;
+ if (!pool->algo)
+ pool->algo = gen_pool_first_fit;
+
+ pool->data = data;
+
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(gen_pool_set_algo);
+
+/**
+ * gen_pool_first_fit - find the first available region
+ * of memory matching the size requirement (no alignment constraint)
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @data: additional data - unused
+ */
+unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
+ unsigned long start, unsigned int nr, void *data)
+{
+ return bitmap_find_next_zero_area(map, size, start, nr, 0);
+}
+EXPORT_SYMBOL(gen_pool_first_fit);
+
+/**
+ * gen_pool_best_fit - find the best fitting region of memory
+ * macthing the size requirement (no alignment constraint)
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @data: additional data - unused
+ *
+ * Iterate over the bitmap to find the smallest free region
+ * which we can allocate the memory.
+ */
+unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
+ unsigned long start, unsigned int nr, void *data)
+{
+ unsigned long start_bit = size;
+ unsigned long len = size + 1;
+ unsigned long index;
+
+ index = bitmap_find_next_zero_area(map, size, start, nr, 0);
+
+ while (index < size) {
+ int next_bit = find_next_bit(map, size, index + nr);
+ if ((next_bit - index) < len) {
+ len = next_bit - index;
+ start_bit = index;
+ if (len == nr)
+ return start_bit;
+ }
+ index = bitmap_find_next_zero_area(map, size,
+ next_bit + 1, nr, 0);
+ }
+
+ return start_bit;
+}
+EXPORT_SYMBOL(gen_pool_best_fit);
--
1.7.10
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists