From 724a493adc3375952739926dc01f8e485b663a1e Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@redhat.com>
Date: Wed, 10 Feb 2016 17:42:07 -0500
Subject: [PATCH] buffer: combine data and buffer::raw into single allocation

Signed-off-by: Sage Weil <sage@redhat.com>
---
 src/common/buffer.cc | 53 ++++++++++++++++++++++++++++++++++++++++++++
 src/include/buffer.h |  2 ++
 2 files changed, 55 insertions(+)

diff --git a/src/common/buffer.cc b/src/common/buffer.cc
index 3c090e4c29499..80a5d513d43d3 100644
--- a/src/common/buffer.cc
+++ b/src/common/buffer.cc
@@ -235,6 +235,34 @@ static simple_spinlock_t buffer_debug_lock = SIMPLE_SPINLOCK_INITIALIZER;
     }
   };
 
+  /*
+   * raw_combined is always placed within a single allocation along
+   * with the data buffer.  the data goes at the beginning, and
+   * raw_combined at the end.  see create_combined.
+   */
+  class buffer::raw_combined : public buffer::raw {
+    size_t alignment;
+  public:
+    raw_combined(char *dataptr, unsigned l, unsigned align=0)
+      : raw(dataptr, l),
+	alignment(align) {
+      inc_total_alloc(len);
+    }
+    ~raw_combined() {
+      dec_total_alloc(len);
+    }
+    raw* clone_empty() {
+      if (alignment)
+	return create_aligned(len, alignment);
+      return create(len);
+    }
+
+    static void operator delete(void *ptr) {
+      raw_combined *raw = (raw_combined *)ptr;
+      ::free((void *)raw->data);
+    }
+  };
+
   class buffer::raw_malloc : public buffer::raw {
   public:
     explicit raw_malloc(unsigned l) : raw(l) {
@@ -654,6 +682,31 @@ static simple_spinlock_t buffer_debug_lock = SIMPLE_SPINLOCK_INITIALIZER;
   buffer::raw* buffer::create_static(unsigned len, char *buf) {
     return new raw_static(buf, len);
   }
+
+  buffer::raw* buffer::create_combined(unsigned len, unsigned align) {
+    if (!align)
+      align = sizeof(size_t);
+    size_t rawlen = ROUND_UP_TO(sizeof(buffer::raw_combined), sizeof(size_t));
+    size_t datalen = ROUND_UP_TO(len, sizeof(size_t));
+
+#ifdef DARWIN
+    char *ptr = (char *) valloc(rawlen + datalen);
+#else
+    char *ptr = 0;
+    int r = ::posix_memalign((void**)(void*)&ptr, align, rawlen + datalen);
+    if (r)
+      throw bad_alloc();
+#endif /* DARWIN */
+    if (!ptr)
+      throw bad_alloc();
+
+    // actual data first, since it has presumably larger alignment restriction
+    // then put the raw_combined at the end
+    raw *ret = new (ptr + datalen) raw_combined(ptr, len, align);
+    assert((char *)ret == ptr + datalen);
+    return ret;
+  }
+
   buffer::raw* buffer::create_aligned(unsigned len, unsigned align) {
 #ifndef __CYGWIN__
     //return new raw_mmap_pages(len);
diff --git a/src/include/buffer.h b/src/include/buffer.h
index c07a82cc26504..81ce336c05a19 100644
--- a/src/include/buffer.h
+++ b/src/include/buffer.h
@@ -136,6 +136,7 @@ namespace buffer CEPH_BUFFER_API {
   class raw_char;
   class raw_pipe;
   class raw_unshareable; // diagnostic, unshareable char buffer
+  class raw_combined;
 
 
   class xio_mempool;
@@ -150,6 +151,7 @@ namespace buffer CEPH_BUFFER_API {
   raw* create_malloc(unsigned len);
   raw* claim_malloc(unsigned len, char *buf);
   raw* create_static(unsigned len, char *buf);
+  raw* create_combined(unsigned len, unsigned align=0);
   raw* create_aligned(unsigned len, unsigned align);
   raw* create_page_aligned(unsigned len);
   raw* create_zero_copy(unsigned len, int fd, int64_t *offset);
-- 
2.39.5