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Align all arrays in mjData's buffer to 64 byte boundaries.

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The introduction of additional mjData arrays for the implicit integrator caused in a shift in data alignment in memory. In certain combinations of machines and models, this change resulted in ~5% performance regression that appears to be attributable to L2 cache misses.

This change aligns all arrays in mjData to the boundary of a typical L2 cache line size. Benchmarking shows that this resolves the performance regression on a Broadwell machine.

PiperOrigin-RevId: 451652783
Change-Id: I4ed2c2d03453a83a0b4a9b8e224e2fd7c0dadea9
This commit is contained in:
Saran Tunyasuvunakool
2022-05-28 13:02:49 -07:00
committed by Copybara-Service
parent 981fa22302
commit 5cc73c30bf
6 changed files with 28 additions and 30 deletions
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src/engine/engine_io.c
+17 -21
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@@ -250,13 +250,9 @@ void mj_defaultStatistic(mjStatistic* stat) {
static const int ID = 54321;
// number of bytes to be skipped to achieve alignment
static unsigned int SKIP(intptr_t offset, unsigned int align) {
// replace structure with int size (mjContact starts with int)
if (align>sizeof(mjtNum)) {
align = sizeof(int);
}
// number of bytes to be skipped to achieve 64-byte alignment
static unsigned int SKIP(intptr_t offset) {
const unsigned int align = 64;
// compute skipped bytes
return (align - (offset % align)) % align;
}
@@ -338,10 +334,10 @@ static void mj_setPtrModel(mjModel* m) {
MJMODEL_POINTERS_PREAMBLE(m);
// assign pointers with padding
#define X(type, name, nr, nc) \
m->name = (type*)(ptr + SKIP((intptr_t)ptr, sizeof(type))); \
ASAN_POISON_MEMORY_REGION(ptr, PTRDIFF(m->name, ptr)); \
ptr += SKIP((intptr_t)ptr, sizeof(type)) + sizeof(type)*(m->nr)*(nc);
#define X(type, name, nr, nc) \
m->name = (type*)(ptr + SKIP((intptr_t)ptr)); \
ASAN_POISON_MEMORY_REGION(ptr, PTRDIFF(m->name, ptr)); \
ptr += SKIP((intptr_t)ptr) + sizeof(type)*(m->nr)*(nc);
MJMODEL_POINTERS
#undef X
@@ -439,9 +435,9 @@ mjModel* mj_makeModel(int nq, int nv, int nu, int na, int nbody, int njnt,
// compute buffer size
m->nbuffer = 0;
#define X(type, name, nr, nc) \
m->nbuffer += SKIP(offset, sizeof(type)) + sizeof(type)*(m->nr)*(nc); \
offset += SKIP(offset, sizeof(type)) + sizeof(type)*(m->nr)*(nc);
#define X(type, name, nr, nc) \
m->nbuffer += SKIP(offset) + sizeof(type)*(m->nr)*(nc); \
offset += SKIP(offset) + sizeof(type)*(m->nr)*(nc);
MJMODEL_POINTERS
#undef X
@@ -763,10 +759,10 @@ static void mj_setPtrData(const mjModel* m, mjData* d) {
MJDATA_POINTERS_PREAMBLE(m);
// assign pointers with padding
#define X(type, name, nr, nc) \
d->name = (type*)(ptr + SKIP((intptr_t)ptr, sizeof(type))); \
ASAN_POISON_MEMORY_REGION(ptr, PTRDIFF(d->name, ptr)); \
ptr += SKIP((intptr_t)ptr, sizeof(type)) + sizeof(type)*(m->nr)*(nc);
#define X(type, name, nr, nc) \
d->name = (type*)(ptr + SKIP((intptr_t)ptr)); \
ASAN_POISON_MEMORY_REGION(ptr, PTRDIFF(d->name, ptr)); \
ptr += SKIP((intptr_t)ptr) + sizeof(type)*(m->nr)*(nc);
MJDATA_POINTERS
#undef X
@@ -795,9 +791,9 @@ static mjData* _makeData(const mjModel* m) {
// compute buffer size
d->nbuffer = 0;
#define X(type, name, nr, nc) \
d->nbuffer += SKIP(offset, sizeof(type)) + sizeof(type)*(m->nr)*(nc); \
offset += SKIP(offset, sizeof(type)) + sizeof(type)*(m->nr)*(nc);
#define X(type, name, nr, nc) \
d->nbuffer += SKIP(offset) + sizeof(type)*(m->nr)*(nc); \
offset += SKIP(offset) + sizeof(type)*(m->nr)*(nc);
MJDATA_POINTERS
#undef X