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[mempool] Apply Unlocked* () functions #5387

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Merged
lewurm merged 1 commit into from
Aug 17, 2017
Merged

[mempool] Apply Unlocked* () functions #5387

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44 changes: 7 additions & 37 deletions mono/metadata/mempool.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@

#include "mempool.h"
#include "mempool-internals.h"
#include "utils/mono-compiler.h"
#include "utils/unlocked.h"

/*
* MonoMemPool is for fast allocation of memory. We free
Expand Down Expand Up @@ -78,7 +78,7 @@ struct _MonoMemPool {
} d;
};

static long total_bytes_allocated = 0;
static gint64 total_bytes_allocated = 0;

/**
* mono_mempool_new:
Expand All @@ -93,19 +93,9 @@ mono_mempool_new (void)

/**
* mono_mempool_new_size:
*
* clang's ThreadSanitizer detects races of total_bytes_allocated and pool->d.allocated throughout the functions
* * mono_mempool_alloc
* * mono_mempool_new_size
* * mono_mempool_destroy
* while these races could lead to wrong values, total_bytes_allocated is just used for debugging / reporting and since
* the mempool.c functions are called quite often, a discussion led the the conclusion of ignoring these races:
* https://bugzilla.xamarin.com/show_bug.cgi?id=57936
*
* \param initial_size the amount of memory to initially reserve for the memory pool.
* \returns a new memory pool with a specific initial memory reservation.
*/
MONO_NO_SANITIZE_THREAD
MonoMemPool *
mono_mempool_new_size (int initial_size)
{
Expand All @@ -125,32 +115,22 @@ mono_mempool_new_size (int initial_size)
pool->pos = (guint8*)pool + SIZEOF_MEM_POOL; // Start after header
pool->end = (guint8*)pool + initial_size; // End at end of allocated space
pool->d.allocated = pool->size = initial_size;
total_bytes_allocated += initial_size;
UnlockedAdd64 (&total_bytes_allocated, initial_size);
return pool;
}

/**
* mono_mempool_destroy:
*
* clang's ThreadSanitizer detects races of total_bytes_allocated and pool->d.allocated throughout the functions
* * mono_mempool_alloc
* * mono_mempool_new_size
* * mono_mempool_destroy
* while these races could lead to wrong values, total_bytes_allocated is just used for debugging / reporting and since
* the mempool.c functions are called quite often, a discussion led the the conclusion of ignoring these races:
* https://bugzilla.xamarin.com/show_bug.cgi?id=57936
*
* \param pool the memory pool to destroy
*
* Free all memory associated with this pool.
*/
MONO_NO_SANITIZE_THREAD
void
mono_mempool_destroy (MonoMemPool *pool)
{
MonoMemPool *p, *n;

total_bytes_allocated -= pool->d.allocated;
UnlockedSubtract64 (&total_bytes_allocated, pool->d.allocated);

p = pool;
while (p) {
Expand Down Expand Up @@ -272,23 +252,13 @@ get_next_size (MonoMemPool *pool, int size)

/**
* mono_mempool_alloc:
*
* clang's ThreadSanitizer detects races of total_bytes_allocated and pool->d.allocated throughout the functions
* * mono_mempool_alloc
* * mono_mempool_new_size
* * mono_mempool_destroy
* while these races could lead to wrong values, total_bytes_allocated is just used for debugging / reporting and since
* the mempool.c functions are called quite often, a discussion led the the conclusion of ignoring these races:
* https://bugzilla.xamarin.com/show_bug.cgi?id=57936
*
* \param pool the memory pool to use
* \param size size of the memory block
*
* Allocates a new block of memory in \p pool .
*
* \returns the address of a newly allocated memory block.
*/
MONO_NO_SANITIZE_THREAD
gpointer
mono_mempool_alloc (MonoMemPool *pool, guint size)
{
Expand Down Expand Up @@ -318,7 +288,7 @@ mono_mempool_alloc (MonoMemPool *pool, guint size)
np->size = new_size;
pool->next = np;
pool->d.allocated += new_size;
total_bytes_allocated += new_size;
UnlockedAdd64 (&total_bytes_allocated, new_size);

rval = (guint8*)np + SIZEOF_MEM_POOL;
} else {
Expand All @@ -332,7 +302,7 @@ mono_mempool_alloc (MonoMemPool *pool, guint size)
pool->pos = (guint8*)np + SIZEOF_MEM_POOL;
pool->end = (guint8*)np + new_size;
pool->d.allocated += new_size;
total_bytes_allocated += new_size;
UnlockedAdd64 (&total_bytes_allocated, new_size);

rval = pool->pos;
pool->pos += size;
Expand Down Expand Up @@ -462,5 +432,5 @@ mono_mempool_get_allocated (MonoMemPool *pool)
long
mono_mempool_get_bytes_allocated (void)
{
return total_bytes_allocated;
return UnlockedRead64 (&total_bytes_allocated);
}
21 changes: 21 additions & 0 deletions mono/utils/unlocked.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,4 +39,25 @@ UnlockedIncrementSize (gsize *val)
return ++*val;
}

MONO_UNLOCKED_ATTRS
gint64
UnlockedAdd64 (gint64 *dest, gint64 add)
{
return *dest += add;
}

MONO_UNLOCKED_ATTRS
gint64
UnlockedSubtract64 (gint64 *dest, gint64 sub)
{
return *dest -= sub;
}

MONO_UNLOCKED_ATTRS
gint64
UnlockedRead64 (gint64 *src)
{
return *src;
}

#endif /* _UNLOCKED_H_ */