Basic mmap based cache for entry mapping only, supporting DRAM<->PMEM…

… cross storage

CMakeLists.txt

@@ -19,7 +19,7 @@ list (REMOVE_DUPLICATES includeDirs)
 add_executable(PMEM_mmap_IO ${sourceFiles})
 target_include_directories(PMEM_mmap_IO PRIVATE ${includeDirs})
 
-set(PMDK_INCLUDE "C:/Users/DEG3NERAT3_/vcpkg/packages/pmdk_x64-windows/include")
-set(PMDK_LIBRARIES "C:/Users/DEG3NERAT3_/vcpkg/packages/pmdk_x64-windows/lib")
-target_include_directories(PMEM_mmap_IO PRIVATE ${PMDK_INCLUDE})
-target_link_libraries(PMEM_mmap_IO PRIVATE ${PMDK_LIBRARIES})
+#set(PMDK_INCLUDE "C:/Users/DEG3NERAT3_/vcpkg/packages/pmdk_x64-windows/include")
+#set(PMDK_LIBRARIES "C:/Users/DEG3NERAT3_/vcpkg/packages/pmdk_x64-windows/lib")
+#target_include_directories(PMEM_mmap_IO PRIVATE ${PMDK_INCLUDE})
+#target_link_libraries(PMEM_mmap_IO PRIVATE ${PMDK_LIBRARIES})

src/main.c

@@ -1,89 +1,37 @@
 #include <stdio.h>
-#include <errno.h>
+#include <sys/mman.h>
 #include <stdlib.h>
-#include <string.h>
-#include <libpmem.h>
+#include "structure/cache.h"
 
-/* using 1k of pmem for this example */
-#define PMEM_LEN 1024
-
-// Maximum length of our buffer
-#define MAX_BUF_LEN 30
-
-/****************************
- * This function writes the "Hello..." string to persistent-memory.
- *****************************/
-void write_hello_string (char *buf, char *path) {
-    char *pmemaddr;
-    size_t mapped_len;
-    int is_pmem;
+int main(int argc, char *argv[]) {
+    cache c;
+    void* entryAlloc = allocateEntries(&c, 5);
 
-    /* create a pmem file and memory map it */
-    if ((pmemaddr = (char *) pmem_map_file(
-            path,
-            PMEM_LEN,
-            PMEM_FILE_CREATE,
-            0666,
-            &mapped_len,
-            &is_pmem
-        )) == NULL) {
-        perror("pmem_map_file");
-        exit(1);
+    if (entryAlloc == MAP_FAILED || entryAlloc == NULL) {
+        printf("Mapping Failed\n");
+        return 1;
     }
-    /* store a string to the persistent memory */
-    strcpy(pmemaddr, buf);
-
-    /* flush above strcpy to persistence */
-    if (is_pmem)
-        pmem_persist(pmemaddr, mapped_len);
-    else
-        pmem_msync(pmemaddr, mapped_len);
 
-    /* output a string from the persistent memory to console */
-    printf("\nWrite the (%s) string to persistent memory.\n",pmemaddr);
-}
-
-/****************************
- * This function reads the "Hello..." string from persistent-memory.
- *****************************/
-void read_hello_string(char *path) {
-    char *pmemaddr;
-    size_t mapped_len;
-    int is_pmem;
-
-    /* open the pmem file to read back the data */
-    if ((pmemaddr = (char *) pmem_map_file(
-            path,
-            PMEM_LEN,
-            PMEM_FILE_CREATE,
-            0666,
-            &mapped_len,
-            &is_pmem
-        )) == NULL) {
-        perror("pmem_map_file");
-        exit(1);
+    int8_t put_result = putEntry(&c, (cache_entry){ .ttl = 100, .value = 42 });
+    if (put_result == -1) {
+        printf("Unable to put entry into cache\n");
+        free(c.entries);
+        return 1;
     }
-    /* Reading the string from persistent-memory and write to console */
-    printf("\nRead the (%s) string from persistent memory.\n",pmemaddr);
-}
 
-/****************************
- * This main function gather from the command line and call the appropriate
- * functions to perform read and write persistently to memory.
- *****************************/
-int main(int argc, char *argv[]) {
-    char *path = argv[2];
+    cache_entry* returned = getEntry(&c, 0);
+    if (returned == NULL) {
+        printf("Could not get entry at index 0 from cache\n");
+        free(c.entries);
+        return 1;
+    }
 
-    // Create the string to save to persistent memory
-    char buf[MAX_BUF_LEN] = "Hello Persistent Memory!!!";
+    printf("Value: %d, TTL: %d\n", returned->value, returned->ttl);
 
-    if (strcmp (argv[1], "-w") == 0) {
-        write_hello_string (buf, path);
-    } else if (strcmp (argv[1], "-r") == 0) {
-        read_hello_string(path);
-    } else {
-        fprintf(stderr, "Usage: %s <-w/-r> <filename>\n", argv[0]);
-        exit(1);
+    if (freeEntries(&c) != 0) {
+        printf("UnMapping Failed\n");
+        return 1;
     }
 
+    return 0;
 }

src/structure/cache.c

@@ -0,0 +1,44 @@
+#include "cache.h"
+#include <stdio.h>
+#include <sys/mman.h>
+
+cache_entry* getEntry(cache* ptr, uint32_t index) {
+    if (ptr == NULL || ptr->count <= index) {
+        return NULL;
+    }
+    return &ptr->entries[index];
+}
+
+int8_t putEntry(cache* ptr, cache_entry entry) {
+    if (ptr == NULL
+        || ptr->count >= ptr->allocatedSize
+        || ptr->entries == NULL
+        || ptr->entries == MAP_FAILED) {
+        return -1;
+    }
+    ptr->entries[ptr->count++] = entry;
+    return 0;
+}
+
+void* allocateEntries(cache* ptr, size_t size) {
+    if (ptr == NULL || size > MAX_CACHE_ENTRIES) {
+        return NULL;
+    }
+    ptr->allocatedSize = size;
+    ptr->count = 0;
+    return ptr->entries = mmap(
+        NULL,
+        size * sizeof(cache_entry),
+        PROT_READ | PROT_WRITE,
+        MAP_PRIVATE | MAP_ANONYMOUS,
+        0,
+        0
+    );
+}
+
+int8_t freeEntries(cache* ptr) {
+    if (ptr == NULL) {
+        return -1;
+    }
+    return munmap(ptr->entries, ptr->allocatedSize * sizeof(cache_entry));
+}

src/structure/cache.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#ifndef PMEM_MMAP_IO_CACHE_H
+#define PMEM_MMAP_IO_CACHE_H
+
+#include <stdint.h>
+#include <stdlib.h>
+#include "entry.h"
+
+#define MAX_CACHE_ENTRIES 10
+
+typedef struct {
+    size_t allocatedSize;
+    size_t count;
+    cache_entry* entries;
+} cache;
+
+cache_entry* getEntry(cache* ptr, uint32_t index);
+int8_t putEntry(cache* ptr, cache_entry entry);
+
+void* allocateEntries(cache* ptr, size_t count);
+int8_t freeEntries(cache* ptr);
+
+#endif //PMEM_MMAP_IO_CACHE_H

src/structure/entry.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#ifndef PMEM_MMAP_IO_ENTRY_H
+#define PMEM_MMAP_IO_ENTRY_H
+
+#include <stdint.h>
+
+typedef struct {
+    uint16_t ttl;
+    int value;
+} cache_entry;
+
+#endif //PMEM_MMAP_IO_ENTRY_H