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Fletcher4: save/reload implementation context
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Init, compute, and fini methods are changed to work on internal context object.
This is necessary because ABI does not guarantee that SIMD registers will be preserved
on function calls. This is technically the case in Linux kernel in between
`kfpu_begin()/kfpu_end()`, but it breaks user-space tests and some kernels that
don't require disabling preemption for using SIMD (osx).

Use scalar compute methods in-place for small buffers, and when the buffer size
does not meet SIMD size alignment.

Signed-off-by: Gvozden Neskovic <[email protected]>
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@ironMann
ironMann committed Oct 5, 2016
1 parent 37f520d commit 5bf703b
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Showing 5 changed files with 303 additions and 194 deletions.
38 changes: 35 additions & 3 deletions include/zfs_fletcher.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -62,12 +62,43 @@ void fletcher_4_init(void);
void fletcher_4_fini(void);



/* Internal fletcher ctx */

typedef struct zfs_fletcher_sse {
uint64_t v[2] __attribute__((aligned(16)));
} zfs_fletcher_sse_t;

typedef struct zfs_fletcher_avx {
uint64_t v[4] __attribute__((aligned(32)));
} zfs_fletcher_avx_t;

typedef struct zfs_fletcher_avx512 {
uint64_t v[8] __attribute__((aligned(64)));
} zfs_fletcher_avx512_t;


typedef union fletcher_4_ctx {
zio_cksum_t scalar;

#if defined(HAVE_SSE2) || (defined(HAVE_SSE2) && defined(HAVE_SSSE3))
zfs_fletcher_sse_t sse[4];
#endif
#if defined(HAVE_AVX) && defined(HAVE_AVX2)
zfs_fletcher_avx_t avx[4];
#endif
#if defined(__x86_64) && defined(HAVE_AVX512F)
zfs_fletcher_avx512_t avx512[4];
#endif
} fletcher_4_ctx_t;

/*
* fletcher checksum struct
*/
typedef void (*fletcher_4_init_f)(zio_cksum_t *);
typedef void (*fletcher_4_fini_f)(zio_cksum_t *);
typedef void (*fletcher_4_compute_f)(const void *, uint64_t, zio_cksum_t *);
typedef void (*fletcher_4_init_f)(fletcher_4_ctx_t *);
typedef void (*fletcher_4_fini_f)(fletcher_4_ctx_t *, zio_cksum_t *);
typedef void (*fletcher_4_compute_f)(fletcher_4_ctx_t *,
const void *, uint64_t);

typedef struct fletcher_4_func {
fletcher_4_init_f init_native;
Expand All @@ -80,6 +111,7 @@ typedef struct fletcher_4_func {
const char *name;
} fletcher_4_ops_t;


#if defined(HAVE_SSE2)
extern const fletcher_4_ops_t fletcher_4_sse2_ops;
#endif
Expand Down
146 changes: 84 additions & 62 deletions module/zcommon/zfs_fletcher.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -138,17 +138,20 @@
#include <zfs_fletcher.h>


static void fletcher_4_scalar_init(zio_cksum_t *zcp);
static void fletcher_4_scalar_native(const void *buf, uint64_t size,
zio_cksum_t *zcp);
static void fletcher_4_scalar_byteswap(const void *buf, uint64_t size,
zio_cksum_t *zcp);
static void fletcher_4_scalar_init(fletcher_4_ctx_t *ctx);
static void fletcher_4_scalar_fini(fletcher_4_ctx_t *ctx, zio_cksum_t *zcp);
static void fletcher_4_scalar_native(fletcher_4_ctx_t *ctx,
const void *buf, uint64_t size);
static void fletcher_4_scalar_byteswap(fletcher_4_ctx_t *ctx,
const void *buf, uint64_t size);
static boolean_t fletcher_4_scalar_valid(void);

static const fletcher_4_ops_t fletcher_4_scalar_ops = {
.init_native = fletcher_4_scalar_init,
.fini_native = fletcher_4_scalar_fini,
.compute_native = fletcher_4_scalar_native,
.init_byteswap = fletcher_4_scalar_init,
.fini_byteswap = fletcher_4_scalar_fini,
.compute_byteswap = fletcher_4_scalar_byteswap,
.valid = fletcher_4_scalar_valid,
.name = "scalar"
Expand Down Expand Up @@ -248,22 +251,29 @@ fletcher_2_byteswap(const void *buf, uint64_t size,
}

static void
fletcher_4_scalar_init(zio_cksum_t *zcp)
fletcher_4_scalar_init(fletcher_4_ctx_t *ctx)
{
ZIO_SET_CHECKSUM(zcp, 0, 0, 0, 0);
ZIO_SET_CHECKSUM(&ctx->scalar, 0, 0, 0, 0);
}

static void
fletcher_4_scalar_fini(fletcher_4_ctx_t *ctx, zio_cksum_t *zcp)
{
memcpy(zcp, &ctx->scalar, sizeof (zio_cksum_t));
}

static void
fletcher_4_scalar_native(const void *buf, uint64_t size, zio_cksum_t *zcp)
fletcher_4_scalar_native(fletcher_4_ctx_t *ctx, const void *buf,
uint64_t size)
{
const uint32_t *ip = buf;
const uint32_t *ipend = ip + (size / sizeof (uint32_t));
uint64_t a, b, c, d;

a = zcp->zc_word[0];
b = zcp->zc_word[1];
c = zcp->zc_word[2];
d = zcp->zc_word[3];
a = ctx->scalar.zc_word[0];
b = ctx->scalar.zc_word[1];
c = ctx->scalar.zc_word[2];
d = ctx->scalar.zc_word[3];

for (; ip < ipend; ip++) {
a += ip[0];
Expand All @@ -272,20 +282,21 @@ fletcher_4_scalar_native(const void *buf, uint64_t size, zio_cksum_t *zcp)
d += c;
}

ZIO_SET_CHECKSUM(zcp, a, b, c, d);
ZIO_SET_CHECKSUM(&ctx->scalar, a, b, c, d);
}

static void
fletcher_4_scalar_byteswap(const void *buf, uint64_t size, zio_cksum_t *zcp)
fletcher_4_scalar_byteswap(fletcher_4_ctx_t *ctx, const void *buf,
uint64_t size)
{
const uint32_t *ip = buf;
const uint32_t *ipend = ip + (size / sizeof (uint32_t));
uint64_t a, b, c, d;

a = zcp->zc_word[0];
b = zcp->zc_word[1];
c = zcp->zc_word[2];
d = zcp->zc_word[3];
a = ctx->scalar.zc_word[0];
b = ctx->scalar.zc_word[1];
c = ctx->scalar.zc_word[2];
d = ctx->scalar.zc_word[3];

for (; ip < ipend; ip++) {
a += BSWAP_32(ip[0]);
Expand All @@ -294,7 +305,7 @@ fletcher_4_scalar_byteswap(const void *buf, uint64_t size, zio_cksum_t *zcp)
d += c;
}

ZIO_SET_CHECKSUM(zcp, a, b, c, d);
ZIO_SET_CHECKSUM(&ctx->scalar, a, b, c, d);
}

static boolean_t
Expand Down Expand Up @@ -384,83 +395,86 @@ fletcher_4_impl_get(void)
}

static inline void
fletcher_4_native_impl(const fletcher_4_ops_t *ops, const void *buf,
uint64_t size, zio_cksum_t *zcp)
fletcher_4_native_impl(const void *buf, uint64_t size, zio_cksum_t *zcp)
{
ops->init_native(zcp);
ops->compute_native(buf, size, zcp);
if (ops->fini_native != NULL)
ops->fini_native(zcp);
fletcher_4_ctx_t ctx;
const fletcher_4_ops_t *ops = fletcher_4_impl_get();

ops->init_native(&ctx);
ops->compute_native(&ctx, buf, size);
ops->fini_native(&ctx, zcp);
}

/*ARGSUSED*/
void
fletcher_4_native(const void *buf, uint64_t size,
const void *ctx_template, zio_cksum_t *zcp)
{
const fletcher_4_ops_t *ops;
uint64_t p2size = P2ALIGN(size, 64);
const uint64_t p2size = P2ALIGN(size, 64);

ASSERT(IS_P2ALIGNED(size, sizeof (uint32_t)));

if (size == 0) {
if (size == 0 || p2size == 0) {
ZIO_SET_CHECKSUM(zcp, 0, 0, 0, 0);
} else if (p2size == 0) {
ops = &fletcher_4_scalar_ops;
fletcher_4_native_impl(ops, buf, size, zcp);

if (size > 0)
fletcher_4_scalar_native((fletcher_4_ctx_t *)zcp,
buf, size);
} else {
ops = fletcher_4_impl_get();
fletcher_4_native_impl(ops, buf, p2size, zcp);
fletcher_4_native_impl(buf, p2size, zcp);

if (p2size < size)
fletcher_4_incremental_native((char *)buf + p2size,
size - p2size, zcp);
fletcher_4_scalar_native((fletcher_4_ctx_t *)zcp,
(char *)buf + p2size, size - p2size);
}
}

void
fletcher_4_native_varsize(const void *buf, uint64_t size, zio_cksum_t *zcp)
{
fletcher_4_native_impl(&fletcher_4_scalar_ops, buf, size, zcp);
ZIO_SET_CHECKSUM(zcp, 0, 0, 0, 0);
fletcher_4_scalar_native((fletcher_4_ctx_t *)zcp, buf, size);
}

static inline void
fletcher_4_byteswap_impl(const fletcher_4_ops_t *ops, const void *buf,
uint64_t size, zio_cksum_t *zcp)
fletcher_4_byteswap_impl(const void *buf, uint64_t size, zio_cksum_t *zcp)
{
ops->init_byteswap(zcp);
ops->compute_byteswap(buf, size, zcp);
if (ops->fini_byteswap != NULL)
ops->fini_byteswap(zcp);
fletcher_4_ctx_t ctx;
const fletcher_4_ops_t *ops = fletcher_4_impl_get();

ops->init_byteswap(&ctx);
ops->compute_byteswap(&ctx, buf, size);
ops->fini_byteswap(&ctx, zcp);
}

/*ARGSUSED*/
void
fletcher_4_byteswap(const void *buf, uint64_t size,
const void *ctx_template, zio_cksum_t *zcp)
{
const fletcher_4_ops_t *ops;
uint64_t p2size = P2ALIGN(size, 64);
const uint64_t p2size = P2ALIGN(size, 64);

ASSERT(IS_P2ALIGNED(size, sizeof (uint32_t)));

if (size == 0) {
if (size == 0 || p2size == 0) {
ZIO_SET_CHECKSUM(zcp, 0, 0, 0, 0);
} else if (p2size == 0) {
ops = &fletcher_4_scalar_ops;
fletcher_4_byteswap_impl(ops, buf, size, zcp);

if (size > 0)
fletcher_4_scalar_byteswap((fletcher_4_ctx_t *)zcp,
buf, size);
} else {
ops = fletcher_4_impl_get();
fletcher_4_byteswap_impl(ops, buf, p2size, zcp);
fletcher_4_byteswap_impl(buf, p2size, zcp);

if (p2size < size)
fletcher_4_incremental_byteswap((char *)buf + p2size,
size - p2size, zcp);
fletcher_4_scalar_byteswap((fletcher_4_ctx_t *)zcp,
(char *)buf + p2size, size - p2size);
}
}

/* Incremental Fletcher 4 */

#define ZFS_FLETCHER_4_INC_MAX_SIZE (8ULL << 20)

static inline void
fletcher_4_incremental_combine(zio_cksum_t *zcp, const uint64_t size,
const zio_cksum_t *nzcp)
Expand All @@ -469,6 +483,13 @@ fletcher_4_incremental_combine(zio_cksum_t *zcp, const uint64_t size,
const uint64_t c2 = c1 * (c1 + 1) / 2;
const uint64_t c3 = c2 * (c1 + 2) / 3;

/*
* Value of 'c3' overflows on buffer sizes close to 16MiB. For that
* reason we split incremental fletcher4 computation of large buffers
* to steps of (ZFS_FLETCHER_4_INC_MAX_SIZE) size.
*/
ASSERT3U(size, <=, ZFS_FLETCHER_4_INC_MAX_SIZE);

zcp->zc_word[3] += nzcp->zc_word[3] + c1 * zcp->zc_word[2] +
c2 * zcp->zc_word[1] + c3 * zcp->zc_word[0];
zcp->zc_word[2] += nzcp->zc_word[2] + c1 * zcp->zc_word[1] +
Expand All @@ -481,13 +502,9 @@ static inline void
fletcher_4_incremental_impl(boolean_t native, const void *buf, uint64_t size,
zio_cksum_t *zcp)
{
static const uint64_t FLETCHER_4_INC_MAX = 8ULL << 20;
uint64_t len;

while (size > 0) {
zio_cksum_t nzc;

len = MIN(size, FLETCHER_4_INC_MAX);
uint64_t len = MIN(size, ZFS_FLETCHER_4_INC_MAX_SIZE);

if (native)
fletcher_4_native(buf, len, NULL, &nzc);
Expand All @@ -504,14 +521,22 @@ fletcher_4_incremental_impl(boolean_t native, const void *buf, uint64_t size,
void
fletcher_4_incremental_native(const void *buf, uint64_t size, zio_cksum_t *zcp)
{
fletcher_4_incremental_impl(B_TRUE, buf, size, zcp);
/* Use scalar impl to directly update cksum of small blocks */
if (size < SPA_MINBLOCKSIZE)
fletcher_4_scalar_native((fletcher_4_ctx_t *)zcp, buf, size);
else
fletcher_4_incremental_impl(B_TRUE, buf, size, zcp);
}

void
fletcher_4_incremental_byteswap(const void *buf, uint64_t size,
zio_cksum_t *zcp)
{
fletcher_4_incremental_impl(B_FALSE, buf, size, zcp);
/* Use scalar impl to directly update cksum of small blocks */
if (size < SPA_MINBLOCKSIZE)
fletcher_4_scalar_byteswap((fletcher_4_ctx_t *)zcp, buf, size);
else
fletcher_4_incremental_impl(B_FALSE, buf, size, zcp);
}


Expand Down Expand Up @@ -662,9 +687,6 @@ fletcher_4_init(void)
membar_producer();

fletcher_4_initialized = B_TRUE;

/* Use 'cycle' math selection method for userspace */
VERIFY0(fletcher_4_impl_set("cycle"));
return;
#endif
/* Benchmark all supported implementations */
Expand Down
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