DAS Interfaces

Interface Description

DAS smart prefetch interfaces.

Interface Format

int32_t Rcache_CeateDasModule(DasModuleParam *createInstanceParam);
void Rcache_ExitDasModule(void);
int32_t Rcache_PutDasInfo(DasKvParam *params);

Parameters

Parameter	Type	Description	Input/Output
createInstanceParam	Pointer to the structure of the callbacks registered by the user	Callbacks to be registered by the user.	Input
params	Pointer to the structure of the I/O information submitted by the user	The user submits I/O information to the smart prefetch interfaces.	Input
ret	Integer	If the interface is successfully invoked, 0 is returned. Otherwise, an error code is returned.	Output

Data Structures

struct DasOPS

Member	Type	Description
SubmitDasPrefetch	Function pointer	Submits prefetch I/Os.
logFunc	Function pointer	Prints DAS internal logs.

struct DasModuleParam

Member	Type	Description
ops	struct DasOPS structure pointer	Callbacks registered by the user.
logger	Pointer	Log module object of the user.
cacheLineSize	Integer	Cache line size.

struct DasKvParam

Member	Type	Description
offset	Integer	Start position of the I/O to be prefetched, in bytes.
len	Integer	Length of the I/O to be prefetched, in bytes.
timeStamp	Integer	I/O timestamp, in nanoseconds.
lunID	Integer	Logical unit ID of the I/O.

Dependency

ksal/das.h

Example

Write DAS test code.

Create a test.cpp file.
```
vi test.cpp
```

Press i to enter the insert mode and add the following test code to the file:

#include <cstdio>
#include <vector>
#include <ksal/das.h>

std::vector<DasKvParam> prefetchInfoLists;

void das_req_prefetch(DasKvParam *params){
    DasKvParam prefetchInfo = {params->offset, params->len, params->timeStamp, params->lunID};
    prefetchInfoLists.push_back(prefetchInfo);
}

void ProducerTask(const uint32_t ioNum)
{
    bool readyToExit = false;
    int32_t ret = 0;
    uint32_t counter = 0;

    for (uint32_t i = 0; i < ioNum; i++){
        DasKvParam params;
        params.offset = 4096 * i;
        params.len = 4096;
        params.timeStamp = 0 + i * 10000000;
        params.lunID = 1;

        ret = Rcache_PutDasInfo(&params);
    }
}

int main(int argc, char **argv)
{
    DasModuleParam *dasInstanceParam = new DasModuleParam();
    dasInstanceParam->cacheLineSize = 8192;
    dasInstanceParam->logger = nullptr;
    DasOPS *regOps = new DasOPS();
    regOps->SubmitDasPrefetch = das_req_prefetch;
    regOps->logFunc = nullptr;
    dasInstanceParam->ops = regOps;
    int32_t ret = Rcache_CeateDasModule(dasInstanceParam);

    uint32_t ioNum = 10000;
    ProducerTask(ioNum);

    for (int i = 0; i < prefetchInfoLists.size(); ++i) {
        printf("prefetchInfo: lunId[%u], offset[%lu], len[%lu]\n", prefetchInfoLists[i].lunID,prefetchInfoLists[i].offset, prefetchInfoLists[i].len);
    }

    Rcache_ExitDasModule();

    return 0;
}

Press Esc to exit the insert mode. Type :wq! and press Enter to save and exit the file.

Compile the test.cpp file into an executable file test.
```
g++ test.cpp -lpthread -ldas -o test
```

Run the test executable file.

./test

The command output is as follows:

config_dasOff: 0
config_dasMemLimit: 300 MB
config_prefetchMaxLen: 16 MB
create DAS module clloector success.
prefetchInfo: lunId[1], offset[20480], len[65536]
prefetchInfo: lunId[1], offset[86016], len[65536]
prefetchInfo: lunId[1], offset[151552], len[65536]
prefetchInfo: lunId[1], offset[217088], len[65536]
prefetchInfo: lunId[1], offset[282624], len[65536]
prefetchInfo: lunId[1], offset[348160], len[65536]
prefetchInfo: lunId[1], offset[413696], len[65536]
prefetchInfo: lunId[1], offset[479232], len[65536]
prefetchInfo: lunId[1], offset[544768], len[65536]
prefetchInfo: lunId[1], offset[610304], len[65536]
prefetchInfo: lunId[1], offset[675840], len[65536]
prefetchInfo: lunId[1], offset[741376], len[65536]
prefetchInfo: lunId[1], offset[806912], len[73728]
prefetchInfo: lunId[1], offset[880640], len[73728]
prefetchInfo: lunId[1], offset[954368], len[81920]
prefetchInfo: lunId[1], offset[1036288], len[81920]
prefetchInfo: lunId[1], offset[1118208], len[90112]
prefetchInfo: lunId[1], offset[1208320], len[90112]
prefetchInfo: lunId[1], offset[1298432], len[98304]
prefetchInfo: lunId[1], offset[1396736], len[98304]
prefetchInfo: lunId[1], offset[1495040], len[106496]
prefetchInfo: lunId[1], offset[1601536], len[106496]
prefetchInfo: lunId[1], offset[1708032], len[114688]
prefetchInfo: lunId[1], offset[1822720], len[114688]
prefetchInfo: lunId[1], offset[1937408], len[122880]
prefetchInfo: lunId[1], offset[2060288], len[122880]
prefetchInfo: lunId[1], offset[2183168], len[131072]
prefetchInfo: lunId[1], offset[2314240], len[131072]
prefetchInfo: lunId[1], offset[2445312], len[139264]
prefetchInfo: lunId[1], offset[2584576], len[139264]
prefetchInfo: lunId[1], offset[2723840], len[147456]
prefetchInfo: lunId[1], offset[2871296], len[147456]
prefetchInfo: lunId[1], offset[3018752], len[155648]
prefetchInfo: lunId[1], offset[3174400], len[155648]
prefetchInfo: lunId[1], offset[3330048], len[163840]
prefetchInfo: lunId[1], offset[3493888], len[163840]
prefetchInfo: lunId[1], offset[3657728], len[172032]
prefetchInfo: lunId[1], offset[3829760], len[172032]
prefetchInfo: lunId[1], offset[4001792], len[180224]
prefetchInfo: lunId[1], offset[4182016], len[180224]
prefetchInfo: lunId[1], offset[4362240], len[188416]
prefetchInfo: lunId[1], offset[4550656], len[360448]
prefetchInfo: lunId[1], offset[4911104], len[720896]
prefetchInfo: lunId[1], offset[5632000], len[1441792]
prefetchInfo: lunId[1], offset[1781760], len[1048576]
prefetchInfo: lunId[1], offset[2830336], len[1048576]
prefetchInfo: lunId[1], offset[3878912], len[1048576]
prefetchInfo: lunId[1], offset[4927488], len[1048576]
prefetchInfo: lunId[1], offset[5976064], len[1048576]
das mem used : 316688 Byte
exit DAS module prefetcher
exit DAS module collector

Parent topic: KSAL Development Reference