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

**Table 1** struct DasOPS
Member	Type	Description
SubmitDasPrefetch	Function pointer	Submits prefetch I/Os.
logFunc	Function pointer	Prints DAS internal logs.

**Table 2** 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.

**Table 3** 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