D3D11 Query查询耗时
确实的来说,这是个Debug/Profile的需求,在运行期这个时间毫无意义,有意义的是两帧之间走过了多少时间,而这个,可以用来查询某一个效果所用耗时,废话不多少,进入正题.
首先要创建查询接口,也就是ID3D11Query* 接口,与查询CPU耗时一样,我们需要三个量,GPU时钟频率,起始时的时间戳,结束时的时间戳.听上去听简单,不过略比CPU的复杂,因为需要通过Begin和End来操作,首先创建三个查询接口:
使用ID3D11Device::CreateQuery函数,函数声明如下:
HRESULT CreateQuery( [in] const D3D11_QUERY_DESC *pQueryDesc,
[out] ID3D11Query **ppQuery
);
我们需要填充一个D3D11_QUERY_DESC结构,来指明查询的内容, D3D11_QUERY_DESC结构如下:
typedef struct D3D11_QUERY_DESC { D3D11_QUERY Query;
UINT MiscFlags;
} D3D11_QUERY_DESC
简单的,将MiscFlags置为0,查询类型有很多种,只捡我们需要的讲,其中一个就是查询时间戳的 D3D11_QUERY_TIMESTAMP,其他的查询,需要在查询之前调用ID3D11Device::Begin,查询之后使用ID3D11Device::End,但是时间戳很明显的不是"一段时间"的查询,而是一个点,所以我们只需要调用End就行了,首先我们就是要获取起始时间戳,意味着创建完查询后,立即调用End,代码如下:
D3D11_QUERY_DESC desc;
desc.Query =D3D11_QUERY_TIMESTAMP;
desc.MiscFlags = 0;
device->CreateQuery(&desc, & timestampstart;
context->End(timestampstart);
这样便获得了起始时间的查询接口,同理,我们还需要创建一个结束时的时间戳查询接口,按照上面的代码再创建一个,然后在结束时调用End,获得数据,所有查询接口的数据通过ID3D11Device::GetData返回,不同的查询接口返回的数据大小不一样,这个函数需要你自己提供一个BUFFER(你得保证有足够的大小),对于D3D11_QUERY_TIMESTAMP,GetData返回的是一个UINT64(windows.h),于是我们需要这样:
std::uint64_t starttime = 0;
while (context->GetData(timestampstart, &starttime, sizeof(starttime), 0) != S_OK)
;
std::uint64_t endtime = 0;
while (context->GetData(timestampend, &endtime, sizeof(endtime), 0) != S_OK)
;
查询不成功可是不断的去循环调用的哦,接下来是查询GPU时钟频率,值得注意的是,这应该不是一个固定值(),使用D3D11_QUERY_TIMESTAMP_DISJOINT 来查询时钟频率,GetData会填充这样一个
typedef struct D3D11_QUERY_DATA_TIMESTAMP_DISJOINT { UINT64 Frequency; BOOL Disjoint; } D3D11_QUERY_DATA_TIMESTAMP_DISJOINT; 结构,很显然,Frequency放的是频率,BOOL变量指示是否有效,如同Disjoint的意思,当其为TRUE的时候,说明时间戳计数因为某些原因而导致了不准确,只有当其为FALSE,查询的两个时间戳之差才是有效的,很显然,加上如下代码:
desc.Query = D3D11_QUERY_TIMESTAMP_DISJOINT;
desc.MiscFlags = 0;
device->CreateQuery(&desc, &disjoint);
注意这个查询需要遵循Begin,End调用,于是,创建完之后,我们应该调用Begin
context->Begin(disjoint);
在查询结束时调用timestampend的End和disjoint的End
context->End(timestampend);
context->End(disjoint);
然后我们就可以获得经过时间了:
std::uint64_t starttime = 0;
while (context->GetData(timestampstart, &starttime, sizeof(starttime), 0) != S_OK)
;
std::uint64_t endtime = 0;
while (context->GetData(timestampend, &endtime, sizeof(endtime), 0) != S_OK)
;
D3D11_QUERY_DATA_TIMESTAMP_DISJOINT disjointdata;
while (context->GetData(disjoint, &disjointdata, sizeof(disjointdata), 0) != S_OK)
;
float time = 0.0f;
if (!disjointdata.Disjoint)
{
std::uint64_t delta = endtime - starttime;
float frequency = static_cast<float>(disjointdata.Frequency);
time = (delta / frequency);
}
为了方便查询,我们可以写个block类,在某个子操作之前构造一个block,构造函数建立一个查询,析构函数结束一个查询.这个block将自己注册在一个查询管理类中,大概就想这样子:
profileblock::profileblock(const std::wstring& name)
:name(name)
{
profiler::global_profiler.startprofile(name);
}
profileblock::~profileblock()
{
profiler::global_profiler.endprofile(name);
}
至于profiler就用一个map,来实现一个字符串对应一个查询
具体实现,我是每5帧才进行一次输出的,但没有取平均时间,代码如下:
//头文件
struct d3d11_timer
{
static const std::uint64_t querylatency = 5;
ID3D11QueryPtr disjoint[querylatency];
ID3D11QueryPtr timestampstart[querylatency];
ID3D11QueryPtr timestampend[querylatency];
bool started{ false };
bool finished{ false };
void start(std::uint64_t currframe,ID3D11Device* device, ID3D11DeviceContext* context);
void end(std::uint64_t currframe, ID3D11DeviceContext* context);
float time(std::uint64_t currframe, ID3D11DeviceContext* context);
};
class profiler
{
public:
static profiler global_profiler;
void init(ID3D11Device* device, ID3D11DeviceContext* context);
void startprofile(const std::wstring& name);
void endprofile(const std::wstring& name);
void endframe();
protected:
static const std::uint64_t querylatency = d3d11_timer::querylatency;
using profilemap = std::map<std::wstring, d3d11_timer>;
profilemap profiles;
std::uint64_t currframe;
ID3D11DevicePtr device;
ID3D11DeviceContextPtr context;
};
class profileblock
{
public:
profileblock(const std::wstring& name);
~profileblock();
protected:
std::wstring name;
};
//源文件
void d3d11_timer::start(std::uint64_t currframe, ID3D11Device* device, ID3D11DeviceContext* context)
{
assert(!started);
assert(!finished);
if (!disjoint[currframe])
{
D3D11_QUERY_DESC desc;
desc.Query = D3D11_QUERY_TIMESTAMP_DISJOINT;
desc.MiscFlags = 0;
//there should checke error and throw exception,but i am not write exception hpp
device->CreateQuery(&desc, &disjoint[currframe]);
desc.Query = D3D11_QUERY_TIMESTAMP;
device->CreateQuery(&desc, ×tampstart[currframe]);
device->CreateQuery(&desc, ×tampend[currframe]);
}
context->Begin(disjoint[currframe]);
context->End(timestampstart[currframe]);
started = true;
}
void d3d11_timer::end(std::uint64_t currframe, ID3D11DeviceContext* context)
{
assert(started);
assert(!finished);
//this mean insert the timestampend
//http://msdn.microsoft.com/en-us/library/windows/desktop/ff476191(v=vs.85).aspx
context->End(timestampend[currframe]);
context->End(disjoint[currframe]);
started = false;
finished = true;
}
float d3d11_timer::time(std::uint64_t currframe, ID3D11DeviceContext* context)
{
if (!finished)
return 0.f;
finished = false;
if (!disjoint[currframe])
return 0.f;
//maybe you can record query time
std::uint64_t starttime = 0;
while (context->GetData(timestampstart[currframe], &starttime, sizeof(starttime), 0) != S_OK)
;
std::uint64_t endtime = 0;
while (context->GetData(timestampend[currframe], &endtime, sizeof(endtime), 0) != S_OK)
;
D3D11_QUERY_DATA_TIMESTAMP_DISJOINT disjointdata;
while (context->GetData(disjoint[currframe], &disjointdata, sizeof(disjointdata), 0) != S_OK)
;
float time = 0.0f;
if (!disjointdata.Disjoint)
{
std::uint64_t delta = endtime - starttime;
float frequency = static_cast<float>(disjointdata.Frequency);
time = (delta / frequency);
}
return time;
}
profiler profiler::global_profiler;
void profiler::init(ID3D11Device* device, ID3D11DeviceContext* context)
{
this->device = device;
this->context = context;
}
void profiler::startprofile(const std::wstring& name)
{
//Todo : query "game setting"
auto & profile = profiles[name];
profile.start(currframe, device, context);
}
void profiler::endprofile(const std::wstring& name)
{
//Todo : query "game setting"
auto & profile = profiles[name];
profile.end(currframe, context);
}
void profiler::endframe()//
{
currframe = (currframe + 1) % querylatency;
//Todo : query "query time"
for (auto iter = profiles.begin(); iter != profiles.end(); ++iter)
{
auto & profile = (*iter).second;
float time = profile.time(currframe, context);
if (time == 0.f)
continue;
DebugPrintf(L"currframe: %u ",currframe);
DebugPrintf(L"%s: %f\n", iter->first.c_str(), time);
}
}
profileblock::profileblock(const std::wstring& name)
:name(name)
{
profiler::global_profiler.startprofile(name);
}
profileblock::~profileblock()
{
profiler::global_profiler.endprofile(name);
}
使用他则是
Void Render()
{
XX();
….
global_profiler.endframe();
}
在XX里面如下
{
Profileblock block("XXX")'
…….
}