1 files changed, 178 insertions, 0 deletions
diff --git a/libnetdata/onewayalloc/onewayalloc.c b/libnetdata/onewayalloc/onewayalloc.c
new file mode 100644
index 00000000..a048aebf
--- /dev/null
+++ b/libnetdata/onewayalloc/onewayalloc.c
@@ -0,0 +1,178 @@
+#include "onewayalloc.h"
+
+static size_t OWA_NATURAL_PAGE_SIZE = 0;
+static size_t OWA_NATURAL_ALIGNMENT = sizeof(int*);
+
+typedef struct owa_page {
+    size_t stats_pages;
+    size_t stats_pages_size;
+    size_t stats_mallocs_made;
+    size_t stats_mallocs_size;
+    size_t size;        // the total size of the page
+    size_t offset;      // the first free byte of the page
+    struct owa_page *next;     // the next page on the list
+    struct owa_page *last;     // the last page on the list - we currently allocate on this
+} OWA_PAGE;
+
+// allocations need to be aligned to CPU register width
+// https://en.wikipedia.org/wiki/Data_structure_alignment
+static inline size_t natural_alignment(size_t size) {
+    if(unlikely(size % OWA_NATURAL_ALIGNMENT))
+        size = size + OWA_NATURAL_ALIGNMENT - (size % OWA_NATURAL_ALIGNMENT);
+
+    return size;
+}
+
+// Create an OWA
+// Once it is created, the called may call the onewayalloc_mallocz()
+// any number of times, for any amount of memory.
+
+static OWA_PAGE *onewayalloc_create_internal(OWA_PAGE *head, size_t size_hint) {
+    if(unlikely(!OWA_NATURAL_PAGE_SIZE))
+        OWA_NATURAL_PAGE_SIZE = sysconf(_SC_PAGE_SIZE);
+
+    // our default page size
+    size_t size = OWA_NATURAL_PAGE_SIZE;
+
+    // make sure the new page will fit both the requested size
+    // and the OWA_PAGE structure at its beginning
+    size_hint += sizeof(OWA_PAGE);
+
+    // prefer the user size if it is bigger than our size
+    if(size_hint > size) size = size_hint;
+
+    // try to allocate half of the total we have allocated already
+    if(likely(head)) {
+        size_t optimal_size = head->stats_pages_size / 2;
+        if(optimal_size > size) size = optimal_size;
+    }
+
+    // Make sure our allocations are always a multiple of the hardware page size
+    if(size % OWA_NATURAL_PAGE_SIZE) size = size + OWA_NATURAL_PAGE_SIZE - (size % OWA_NATURAL_PAGE_SIZE);
+
+    // OWA_PAGE *page = (OWA_PAGE *)netdata_mmap(NULL, size, MAP_ANONYMOUS|MAP_PRIVATE, 0);
+    // if(unlikely(!page)) fatal("Cannot allocate onewayalloc buffer of size %zu", size);
+    OWA_PAGE *page = (OWA_PAGE *)mallocz(size);
+
+    page->size = size;
+    page->offset = natural_alignment(sizeof(OWA_PAGE));
+    page->next = page->last = NULL;
+
+    if(unlikely(!head)) {
+        // this is the first time we are called
+        head = page;
+        head->stats_pages = 0;
+        head->stats_pages_size = 0;
+        head->stats_mallocs_made = 0;
+        head->stats_mallocs_size = 0;
+    }
+    else {
+        // link this page into our existing linked list
+        head->last->next = page;
+    }
+
+    head->last = page;
+    head->stats_pages++;
+    head->stats_pages_size += size;
+
+    return (ONEWAYALLOC *)page;
+}
+
+ONEWAYALLOC *onewayalloc_create(size_t size_hint) {
+    return onewayalloc_create_internal(NULL, size_hint);
+}
+
+void *onewayalloc_mallocz(ONEWAYALLOC *owa, size_t size) {
+    OWA_PAGE *head = (OWA_PAGE *)owa;
+    OWA_PAGE *page = head->last;
+
+    // update stats
+    head->stats_mallocs_made++;
+    head->stats_mallocs_size += size;
+
+    // make sure the size is aligned
+    size = natural_alignment(size);
+
+    if(unlikely(page->size - page->offset < size)) {
+        // we don't have enough space to fit the data
+        // let's get another page
+        page = onewayalloc_create_internal(head, (size > page->size)?size:page->size);
+    }
+
+    char *mem = (char *)page;
+    mem = &mem[page->offset];
+    page->offset += size;
+
+    return (void *)mem;
+}
+
+void *onewayalloc_callocz(ONEWAYALLOC *owa, size_t nmemb, size_t size) {
+    size_t total = nmemb * size;
+    void *mem = onewayalloc_mallocz(owa, total);
+    memset(mem, 0, total);
+    return mem;
+}
+
+char *onewayalloc_strdupz(ONEWAYALLOC *owa, const char *s) {
+    size_t size = strlen(s) + 1;
+    char *d = onewayalloc_mallocz((OWA_PAGE *)owa, size);
+    memcpy(d, s, size);
+    return d;
+}
+
+void *onewayalloc_memdupz(ONEWAYALLOC *owa, const void *src, size_t size) {
+    void *mem = onewayalloc_mallocz((OWA_PAGE *)owa, size);
+    // memcpy() is way faster than strcpy() since it does not check for '\0'
+    memcpy(mem, src, size);
+    return mem;
+}
+
+void onewayalloc_freez(ONEWAYALLOC *owa __maybe_unused, const void *ptr __maybe_unused) {
+#ifdef NETDATA_INTERNAL_CHECKS
+    // allow the caller to call us for a mallocz() allocation
+    // so try to find it in our memory and if it is not there
+    // log an error
+
+    if (unlikely(!ptr))
+        return;
+
+    OWA_PAGE *head = (OWA_PAGE *)owa;
+    OWA_PAGE *page;
+    size_t seeking = (size_t)ptr;
+
+    for(page = head; page ;page = page->next) {
+        size_t start = (size_t)page;
+        size_t end = start + page->size;
+
+        if(seeking >= start && seeking <= end) {
+            // found it - it is ours
+            // just return to let the caller think we actually did something
+            return;
+        }
+    }
+
+    // not found - it is not ours
+    // let's free it with the system allocator
+    error("ONEWAYALLOC: request to free address 0x%p that is not allocated by this OWA", ptr);
+#endif
+
+    return;
+}
+
+void onewayalloc_destroy(ONEWAYALLOC *owa) {
+    if(!owa) return;
+
+    OWA_PAGE *head = (OWA_PAGE *)owa;
+
+    //info("OWA: %zu allocations of %zu total bytes, in %zu pages of %zu total bytes",
+    //     head->stats_mallocs_made, head->stats_mallocs_size,
+    //     head->stats_pages, head->stats_pages_size);
+
+    OWA_PAGE *page = head;
+    while(page) {
+        OWA_PAGE *p = page;
+        page = page->next;
+        // munmap(p, p->size);
+        freez(p);
+    }
+}