[Mesa-dev] [PATCH] anv: implement pipeline statistics queries
Ilia Mirkin
imirkin at alum.mit.edu
Wed Feb 22 05:40:08 UTC 2017
On Wed, Feb 22, 2017 at 12:07 AM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> Hey Look. I'm actually reading your patch now!
>
> I read through the whole thing and over-all I think it looks fairly good.
>
> On Sun, Nov 27, 2016 at 11:23 AM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>
>> The strategy is to just keep n anv_query_pool_slot entries per query
>> instead of one. The available bit is only valid in the last one.
>
>
> Seems like a reasonable approach. To be honest, I'm not a huge fan of the
> "available" bit (or 64 bits as the case may be) but I'm not sure how we'd
> get away without it.
>
> Maybe it would be better to do something like:
>
> struct anv_query_entry {
> uint64_t begin;
> uint64_t end;
> };
>
> struct anv_query_pool_slot {
> uint64_t available
> struct anv_query_entry entries[0];
> };
>
> Food for thought.
Seems reasonable.
>
>>
>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> ---
>>
>> I think this is in a pretty good state now. I've tested both the direct
>> and
>> buffer paths with a hacked up cube application, and I'm seeing
>> non-ridiculous
>> values for the various counters, although I haven't 100% verified them for
>> accuracy.
>>
>> This also implements the hsw/bdw workaround for dividing frag invocations
>> by 4,
>> copied from hsw_queryobj. I tested this on SKL and it seem to divide the
>> values
>> as expected.
>>
>> The cube patch I've been testing with is at
>> http://paste.debian.net/899374/
>> You can flip between copying to a buffer and explicit retrieval by
>> commenting
>> out the relevant function calls.
>>
>> src/intel/vulkan/anv_device.c | 2 +-
>> src/intel/vulkan/anv_private.h | 4 +
>> src/intel/vulkan/anv_query.c | 99 ++++++++++----
>> src/intel/vulkan/genX_cmd_buffer.c | 260
>> ++++++++++++++++++++++++++++++++-----
>> 4 files changed, 308 insertions(+), 57 deletions(-)
>>
>> diff --git a/src/intel/vulkan/anv_device.c b/src/intel/vulkan/anv_device.c
>> index 99eb73c..7ad1970 100644
>> --- a/src/intel/vulkan/anv_device.c
>> +++ b/src/intel/vulkan/anv_device.c
>> @@ -427,7 +427,7 @@ void anv_GetPhysicalDeviceFeatures(
>> .textureCompressionASTC_LDR = pdevice->info.gen >= 9,
>> /* FINISHME CHV */
>> .textureCompressionBC = true,
>> .occlusionQueryPrecise = true,
>> - .pipelineStatisticsQuery = false,
>> + .pipelineStatisticsQuery = true,
>> .fragmentStoresAndAtomics = true,
>> .shaderTessellationAndGeometryPointSize = true,
>> .shaderImageGatherExtended = false,
>> diff --git a/src/intel/vulkan/anv_private.h
>> b/src/intel/vulkan/anv_private.h
>> index 2fc543d..7271609 100644
>> --- a/src/intel/vulkan/anv_private.h
>> +++ b/src/intel/vulkan/anv_private.h
>> @@ -1763,6 +1763,8 @@ struct anv_render_pass {
>> struct anv_subpass subpasses[0];
>> };
>>
>> +#define ANV_PIPELINE_STATISTICS_COUNT 11
>> +
>> struct anv_query_pool_slot {
>> uint64_t begin;
>> uint64_t end;
>> @@ -1772,6 +1774,8 @@ struct anv_query_pool_slot {
>> struct anv_query_pool {
>> VkQueryType type;
>> uint32_t slots;
>> + uint32_t pipeline_statistics;
>> + uint32_t slot_stride;
>> struct anv_bo bo;
>> };
>>
>> diff --git a/src/intel/vulkan/anv_query.c b/src/intel/vulkan/anv_query.c
>> index 293257b..dc00859 100644
>> --- a/src/intel/vulkan/anv_query.c
>> +++ b/src/intel/vulkan/anv_query.c
>> @@ -38,8 +38,10 @@ VkResult anv_CreateQueryPool(
>> ANV_FROM_HANDLE(anv_device, device, _device);
>> struct anv_query_pool *pool;
>> VkResult result;
>> - uint32_t slot_size;
>> - uint64_t size;
>> + uint32_t slot_size = sizeof(struct anv_query_pool_slot);
>>
>> + uint32_t slot_stride = 1;
>
>
> Strides are usually in bytes, not slots...
slot_pitch? :) IMHO stride/pitch doesn't have a unit implied by the
name itself. I'm pretty sure I've seen it refer to both bytes and
higher-level units.
>
>>
>> + uint64_t size = pCreateInfo->queryCount * slot_size;
>
>
> Might make sense to move this to after we compute the slot_stride.
>
>>
>> + uint32_t pipeline_statistics = 0;
>>
>> assert(pCreateInfo->sType ==
>> VK_STRUCTURE_TYPE_QUERY_POOL_CREATE_INFO);
>>
>> @@ -48,12 +50,16 @@ VkResult anv_CreateQueryPool(
>> case VK_QUERY_TYPE_TIMESTAMP:
>> break;
>> case VK_QUERY_TYPE_PIPELINE_STATISTICS:
>> - return VK_ERROR_INCOMPATIBLE_DRIVER;
>> + pipeline_statistics = pCreateInfo->pipelineStatistics &
>> + ((1 << ANV_PIPELINE_STATISTICS_COUNT) - 1);
>> + slot_stride = _mesa_bitcount(pipeline_statistics);
>> + size *= slot_stride;
>> + break;
>> default:
>> assert(!"Invalid query type");
>> + return VK_ERROR_INCOMPATIBLE_DRIVER;
>> }
>>
>> - slot_size = sizeof(struct anv_query_pool_slot);
>> pool = vk_alloc2(&device->alloc, pAllocator, sizeof(*pool), 8,
>> VK_SYSTEM_ALLOCATION_SCOPE_OBJECT);
>> if (pool == NULL)
>> @@ -61,8 +67,9 @@ VkResult anv_CreateQueryPool(
>>
>> pool->type = pCreateInfo->queryType;
>> pool->slots = pCreateInfo->queryCount;
>> + pool->pipeline_statistics = pipeline_statistics;
>> + pool->slot_stride = slot_stride;
>>
>> - size = pCreateInfo->queryCount * slot_size;
>> result = anv_bo_init_new(&pool->bo, device, size);
>> if (result != VK_SUCCESS)
>> goto fail;
>> @@ -95,6 +102,27 @@ void anv_DestroyQueryPool(
>> vk_free2(&device->alloc, pAllocator, pool);
>> }
>>
>> +static void *
>> +store_query_result(void *pData, VkQueryResultFlags flags,
>> + uint64_t result, uint64_t available)
>> +{
>> + if (flags & VK_QUERY_RESULT_64_BIT) {
>> + uint64_t *dst = pData;
>> + *dst++ = result;
>> + if (flags & VK_QUERY_RESULT_WITH_AVAILABILITY_BIT)
>> + *dst++ = available;
>> + return dst;
>> + } else {
>> + uint32_t *dst = pData;
>> + if (result > UINT32_MAX)
>> + result = UINT32_MAX;
>> + *dst++ = result;
>> + if (flags & VK_QUERY_RESULT_WITH_AVAILABILITY_BIT)
>> + *dst++ = available;
>> + return dst;
>> + }
>> +}
>> +
>> VkResult anv_GetQueryPoolResults(
>> VkDevice _device,
>> VkQueryPool queryPool,
>> @@ -112,6 +140,7 @@ VkResult anv_GetQueryPoolResults(
>> int ret;
>>
>> assert(pool->type == VK_QUERY_TYPE_OCCLUSION ||
>> + pool->type == VK_QUERY_TYPE_PIPELINE_STATISTICS ||
>> pool->type == VK_QUERY_TYPE_TIMESTAMP);
>>
>> if (pData == NULL)
>> @@ -129,14 +158,42 @@ VkResult anv_GetQueryPoolResults(
>> void *data_end = pData + dataSize;
>> struct anv_query_pool_slot *slot = pool->bo.map;
>>
>> - for (uint32_t i = 0; i < queryCount; i++) {
>> + for (uint32_t i = 0; i < queryCount && pData < data_end;
>
>
> I think this condition is broken if dataSize is not a multiple of the query
> slot stride.
Urgh yeah. But fixable by adjusting the data_end pointer.
>
>>
>> + i++, pData += stride) {
>> + if (pool->type == VK_QUERY_TYPE_PIPELINE_STATISTICS) {
>> + VkQueryResultFlags f = flags &
>> ~VK_QUERY_RESULT_WITH_AVAILABILITY_BIT;
>> + void *pos = pData;
>> + uint32_t pipeline_statistics = pool->pipeline_statistics;
>> + struct anv_query_pool_slot *base =
>> + &slot[(firstQuery + i) * pool->slot_stride];
>> +
>> + while (pipeline_statistics) {
>> + uint32_t stat = u_bit_scan(&pipeline_statistics);
>> + uint64_t result = base->end - base->begin;
>> +
>> + /* WaDividePSInvocationCountBy4:HSW,BDW */
>> + if ((device->info.gen == 8 || device->info.is_haswell) &&
>> + (1 << stat) ==
>> VK_QUERY_PIPELINE_STATISTIC_FRAGMENT_SHADER_INVOCATIONS_BIT)
>> + result >>= 2;
>> +
>> + pos = store_query_result(pos, f, result, 0);
>>
>> + base++;
>> + }
>> + if (flags & VK_QUERY_RESULT_WITH_AVAILABILITY_BIT) {
>> + base--;
>> + if (flags & VK_QUERY_RESULT_64_BIT)
>> + *(uint64_t *)pos = base->available;
>> + else
>> + *(uint32_t *)pos = base->available;
>
>
> Given what I'm reading here, I think my suggestion above about reworking
> query_slot makes even more sense.
>
>>
>> + }
>> + continue;
>> + }
>> +
>> switch (pool->type) {
>> case VK_QUERY_TYPE_OCCLUSION: {
>> result = slot[firstQuery + i].end - slot[firstQuery + i].begin;
>> break;
>> }
>> - case VK_QUERY_TYPE_PIPELINE_STATISTICS:
>> - unreachable("pipeline stats not supported");
>> case VK_QUERY_TYPE_TIMESTAMP: {
>> result = slot[firstQuery + i].begin;
>> break;
>> @@ -145,23 +202,7 @@ VkResult anv_GetQueryPoolResults(
>> unreachable("invalid pool type");
>> }
>>
>> - if (flags & VK_QUERY_RESULT_64_BIT) {
>> - uint64_t *dst = pData;
>> - dst[0] = result;
>> - if (flags & VK_QUERY_RESULT_WITH_AVAILABILITY_BIT)
>> - dst[1] = slot[firstQuery + i].available;
>> - } else {
>> - uint32_t *dst = pData;
>> - if (result > UINT32_MAX)
>> - result = UINT32_MAX;
>> - dst[0] = result;
>> - if (flags & VK_QUERY_RESULT_WITH_AVAILABILITY_BIT)
>> - dst[1] = slot[firstQuery + i].available;
>> - }
>> -
>> - pData += stride;
>> - if (pData >= data_end)
>> - break;
>> + store_query_result(pData, flags, result, slot[firstQuery +
>> i].available);
>> }
>>
>> return VK_SUCCESS;
>> @@ -183,6 +224,14 @@ void anv_CmdResetQueryPool(
>> slot[firstQuery + i].available = 0;
>> break;
>> }
>> + case VK_QUERY_TYPE_PIPELINE_STATISTICS: {
>> + struct anv_query_pool_slot *slot = pool->bo.map;
>> +
>> + slot = &slot[(firstQuery + i) * pool->slot_stride];
>> + for (uint32_t j = 0; j < pool->slot_stride; j++)
>> + slot[j].available = 0;
>> + break;
>> + }
>> default:
>> assert(!"Invalid query type");
>> }
>> diff --git a/src/intel/vulkan/genX_cmd_buffer.c
>> b/src/intel/vulkan/genX_cmd_buffer.c
>> index a965cd6..1369ac2 100644
>> --- a/src/intel/vulkan/genX_cmd_buffer.c
>> +++ b/src/intel/vulkan/genX_cmd_buffer.c
>> @@ -2272,6 +2272,50 @@ emit_query_availability(struct anv_cmd_buffer
>> *cmd_buffer,
>> }
>> }
>>
>> +#define IA_VERTICES_COUNT 0x2310
>> +#define IA_PRIMITIVES_COUNT 0x2318
>> +#define VS_INVOCATION_COUNT 0x2320
>> +#define HS_INVOCATION_COUNT 0x2300
>> +#define DS_INVOCATION_COUNT 0x2308
>> +#define GS_INVOCATION_COUNT 0x2328
>> +#define GS_PRIMITIVES_COUNT 0x2330
>> +#define CL_INVOCATION_COUNT 0x2338
>> +#define CL_PRIMITIVES_COUNT 0x2340
>> +#define PS_INVOCATION_COUNT 0x2348
>> +#define CS_INVOCATION_COUNT 0x2290
>
>
> I think the "right" thing to do would be to add genxml for these.
I actually started out by doing that. But it seemed excessive given
that these are the same in each generation. OTOH this is in a genX_*
file, so it's getting compiled N times anyways, so there's no
additional overhead from it...
>
>>
>> +
>> +static const uint32_t PIPELINE_STAT_TO_REG[] = {
>> + IA_VERTICES_COUNT,
>> + IA_PRIMITIVES_COUNT,
>> + VS_INVOCATION_COUNT,
>> + GS_INVOCATION_COUNT,
>> + GS_PRIMITIVES_COUNT,
>> + CL_INVOCATION_COUNT,
>> + CL_PRIMITIVES_COUNT,
>> + PS_INVOCATION_COUNT,
>> + HS_INVOCATION_COUNT,
>> + DS_INVOCATION_COUNT,
>> + CS_INVOCATION_COUNT
>> +};
>> +
>> +static void
>> +emit_pipeline_stat(struct anv_cmd_buffer *cmd_buffer, uint32_t stat,
>> + struct anv_bo *bo, uint32_t offset) {
>> + STATIC_ASSERT(ARRAY_SIZE(PIPELINE_STAT_TO_REG) ==
>> + ANV_PIPELINE_STATISTICS_COUNT);
>> +
>> + uint32_t reg = PIPELINE_STAT_TO_REG[stat];
>> +
>> + anv_batch_emit(&cmd_buffer->batch, GENX(MI_STORE_REGISTER_MEM), lrm) {
>> + lrm.RegisterAddress = reg,
>> + lrm.MemoryAddress = (struct anv_address) { bo, offset };
>> + }
>> + anv_batch_emit(&cmd_buffer->batch, GENX(MI_STORE_REGISTER_MEM), lrm) {
>> + lrm.RegisterAddress = reg + 4,
>> + lrm.MemoryAddress = (struct anv_address) { bo, offset + 4 };
>> + }
>> +}
>> +
>> void genX(CmdBeginQuery)(
>> VkCommandBuffer commandBuffer,
>> VkQueryPool queryPool,
>> @@ -2301,7 +2345,25 @@ void genX(CmdBeginQuery)(
>> query * sizeof(struct anv_query_pool_slot));
>> break;
>>
>> - case VK_QUERY_TYPE_PIPELINE_STATISTICS:
>> + case VK_QUERY_TYPE_PIPELINE_STATISTICS: {
>> + uint32_t pipeline_statistics = pool->pipeline_statistics;
>> + uint32_t slot_offset = query * pool->slot_stride *
>> + sizeof(struct anv_query_pool_slot);
>> +
>> + /* TODO: This might only be necessary for certain stats */
>> + anv_batch_emit(&cmd_buffer->batch, GENX(PIPE_CONTROL), pc) {
>> + pc.CommandStreamerStallEnable = true;
>> + pc.StallAtPixelScoreboard = true;
>> + }
>> +
>> + while (pipeline_statistics) {
>> + uint32_t stat = u_bit_scan(&pipeline_statistics);
>> +
>> + emit_pipeline_stat(cmd_buffer, stat, &pool->bo, slot_offset);
>> + slot_offset += sizeof(struct anv_query_pool_slot);
>> + }
>> + break;
>> + }
>> default:
>> unreachable("");
>> }
>> @@ -2314,17 +2376,35 @@ void genX(CmdEndQuery)(
>> {
>> ANV_FROM_HANDLE(anv_cmd_buffer, cmd_buffer, commandBuffer);
>> ANV_FROM_HANDLE(anv_query_pool, pool, queryPool);
>> + uint32_t slot_offset = query * pool->slot_stride *
>> + sizeof(struct anv_query_pool_slot);
>>
>> switch (pool->type) {
>> case VK_QUERY_TYPE_OCCLUSION:
>> - emit_ps_depth_count(cmd_buffer, &pool->bo,
>> - query * sizeof(struct anv_query_pool_slot) +
>> 8);
>> + emit_ps_depth_count(cmd_buffer, &pool->bo, slot_offset + 8);
>> + emit_query_availability(cmd_buffer, &pool->bo, slot_offset + 16);
>> + break;
>> +
>> + case VK_QUERY_TYPE_PIPELINE_STATISTICS: {
>> + uint32_t pipeline_statistics = pool->pipeline_statistics;
>> + /* TODO: This might only be necessary for certain stats */
>> + anv_batch_emit(&cmd_buffer->batch, GENX(PIPE_CONTROL), pc) {
>> + pc.CommandStreamerStallEnable = true;
>> + pc.StallAtPixelScoreboard = true;
>> + }
>> +
>> + while (pipeline_statistics) {
>> + uint32_t stat = u_bit_scan(&pipeline_statistics);
>>
>> - emit_query_availability(cmd_buffer, &pool->bo,
>> - query * sizeof(struct anv_query_pool_slot)
>> + 16);
>> + emit_pipeline_stat(cmd_buffer, stat, &pool->bo, slot_offset +
>> 8);
>> + slot_offset += sizeof(struct anv_query_pool_slot);
>> + }
>> +
>> + slot_offset -= sizeof(struct anv_query_pool_slot);
>> + emit_query_availability(cmd_buffer, &pool->bo, slot_offset + 16);
>> break;
>> + }
>>
>> - case VK_QUERY_TYPE_PIPELINE_STATISTICS:
>> default:
>> unreachable("");
>> }
>> @@ -2421,6 +2501,31 @@ emit_load_alu_reg_u64(struct anv_batch *batch,
>> uint32_t reg,
>> }
>>
>> static void
>> +emit_load_alu_reg_imm32(struct anv_batch *batch, uint32_t reg, uint32_t
>> imm)
>> +{
>> + anv_batch_emit(batch, GENX(MI_LOAD_REGISTER_IMM), lri) {
>> + lri.RegisterOffset = reg;
>> + lri.DataDWord = imm;
>> + }
>> +}
>> +
>> +static void
>> +emit_load_alu_reg_imm64(struct anv_batch *batch, uint32_t reg, uint64_t
>> imm)
>> +{
>> + emit_load_alu_reg_imm32(batch, reg, (uint32_t)imm);
>> + emit_load_alu_reg_imm32(batch, reg + 4, (uint32_t)(imm >> 32));
>
>
> I don't think the casts are needed here. They don't hurt though.
It probably made me feel slightly better. You're, of course, right -
they're unnecessary. Conceivable that I copied it out of somewhere but
I don't see immediately where.
>
>>
>> +}
>> +
>> +static void
>> +emit_load_alu_reg_reg32(struct anv_batch *batch, uint32_t src, uint32_t
>> dst)
>> +{
>> + anv_batch_emit(batch, GENX(MI_LOAD_REGISTER_REG), lrr) {
>> + lrr.SourceRegisterAddress = src;
>> + lrr.DestinationRegisterAddress = dst;
>> + }
>> +}
>> +
>> +static uint32_t
>> store_query_result(struct anv_batch *batch, uint32_t reg,
>> struct anv_bo *bo, uint32_t offset, VkQueryResultFlags
>> flags)
>> {
>> @@ -2434,9 +2539,88 @@ store_query_result(struct anv_batch *batch,
>> uint32_t reg,
>> srm.RegisterAddress = reg + 4;
>> srm.MemoryAddress = (struct anv_address) { bo, offset + 4 };
>> }
>> +
>> + return offset + 8;
>> + }
>> +
>> + return offset + 4;
>> +}
>> +
>> +/*
>> + * GPR0 = GPR0 & ((1ull << n) - 1);
>> + */
>> +static void
>> +keep_gpr0_lower_n_bits(struct anv_batch *batch, uint32_t n)
>> +{
>> + assert(n < 64);
>> + emit_load_alu_reg_imm64(batch, CS_GPR(1), (1ull << n) - 1);
>> +
>> + uint32_t *dw = anv_batch_emitn(batch, 5, GENX(MI_MATH));
>> + dw[1] = alu(OPCODE_LOAD, OPERAND_SRCA, OPERAND_R0);
>> + dw[2] = alu(OPCODE_LOAD, OPERAND_SRCB, OPERAND_R1);
>> + dw[3] = alu(OPCODE_AND, 0, 0);
>> + dw[4] = alu(OPCODE_STORE, OPERAND_R0, OPERAND_ACCU);
>> +}
>> +
>> +/*
>> + * GPR0 = GPR0 << 30;
>> + */
>> +static void
>> +shl_gpr0_by_30_bits(struct anv_batch *batch)
>> +{
>> + /* First we mask 34 bits of GPR0 to prevent overflow */
>> + keep_gpr0_lower_n_bits(batch, 34);
>> +
>> + const uint32_t outer_count = 5;
>> + const uint32_t inner_count = 6;
>> + STATIC_ASSERT(outer_count * inner_count == 30);
>> + const uint32_t cmd_len = 1 + inner_count * 4;
>> +
>> + /* We'll emit 5 commands, each shifting GPR0 left by 6 bits, for a
>> total of
>> + * 30 left shifts.
>
>
> Why do we need 5 MI_MATH commands? Can't we do it in 1?
Just copying code from hsw_queryobj. Perhaps there's a limit on the
number of MI_MATH commands in one batch. Or there are other reasons
for it? Either way, I haven't the faintest clue.
>
>>
>> + */
>> + for (int o = 0; o < outer_count; o++) {
>> + /* Submit one MI_MATH to shift left by 6 bits */
>> + uint32_t *dw = anv_batch_emitn(batch, cmd_len, GENX(MI_MATH));
>> + dw++;
>> + for (int i = 0; i < inner_count; i++, dw += 4) {
>> + dw[0] = alu(OPCODE_LOAD, OPERAND_SRCA, OPERAND_R0);
>> + dw[1] = alu(OPCODE_LOAD, OPERAND_SRCB, OPERAND_R0);
>> + dw[2] = alu(OPCODE_ADD, 0, 0);
>> + dw[3] = alu(OPCODE_STORE, OPERAND_R0, OPERAND_ACCU);
>> + }
>> }
>> }
>>
>> +/*
>> + * GPR0 = GPR0 >> 2;
>> + *
>> + * Note that the upper 30 bits of GPR are lost!
>> + */
>> +static void
>> +shr_gpr0_by_2_bits(struct anv_batch *batch)
>> +{
>> + shl_gpr0_by_30_bits(batch);
>> + emit_load_alu_reg_reg32(batch, CS_GPR(0) + 4, CS_GPR(0));
>> + emit_load_alu_reg_imm32(batch, CS_GPR(0) + 4, 0);
>> +}
>> +
>> +static void
>> +compute_query_result(struct anv_batch *batch, struct anv_bo *bo,
>> + uint32_t dst_reg, uint32_t offset)
>> +{
>> + emit_load_alu_reg_u64(batch, CS_GPR(0), bo, offset);
>> + emit_load_alu_reg_u64(batch, CS_GPR(1), bo, offset + 8);
>> +
>> + /* FIXME: We need to clamp the result for 32 bit. */
>> +
>> + uint32_t *dw = anv_batch_emitn(batch, 5, GENX(MI_MATH));
>> + dw[1] = alu(OPCODE_LOAD, OPERAND_SRCA, OPERAND_R1);
>> + dw[2] = alu(OPCODE_LOAD, OPERAND_SRCB, OPERAND_R0);
>> + dw[3] = alu(OPCODE_SUB, 0, 0);
>> + dw[4] = alu(OPCODE_STORE, dst_reg, OPERAND_ACCU);
>> +}
>
>
> Ugh... So, I've been thinking about this a bit and I'm actually starting to
> wonder if we don't want to take a completely different approach to
> CmdCopyQueryPoolResults. Namely, to use a vertex shader and
> trandform-feedback to pull query buffer data in one end and dump computed
> query results out the other. For small quantities of queries, the command
> streamer math may be faster, but if they're pulling a lot of queries, a VS
> may be more efficient. Also, it's way more flexible in terms of the math it
> allows you to do. Talos pulls queries in blocks of 256. If you were to try
> and pull that many pipeline statistics queries, the amount of batch space it
> would burn is insane.
>
> I'm happy to be the one to play with this. I'm also reasonably happy to
> land all the CS math and then clean it up later with a VS if it turns out to
> be the most practical path. Thoughts?
Using a shader (vertex or compute) is an approach that I believe
radeonsi takes for these query buffers. I've been able to avoid it for
nouveau's qbo implementation thus far (there are a handful of
failures, but they're largely my own laziness rather than an issue
with the approach).
This is all you (or anyone else who feels like it) - like I said, I
consider this patch abandoned on my end. Feel free to use all, some,
or none of it. It's still available at
https://github.com/imirkin/mesa/commits/anv in case you need it in git
form.
Cheers,
-ilia
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