From 437f4c75d413049165a6e627f2a0cefb85ec0afb Mon Sep 17 00:00:00 2001
From: Maksim Andrianov <maksimandrianov1@gmail.com>
Date: Fri, 26 Feb 2021 05:46:16 +0300
Subject: [coding] Added madvise for MmapReader.

---
 coding/mmap_reader.cpp          | 35 ++++++++++++++++++++++++-----------
 coding/mmap_reader.hpp          |  9 ++++++++-
 generator/intermediate_data.cpp |  4 ++--
 3 files changed, 34 insertions(+), 14 deletions(-)

diff --git a/coding/mmap_reader.cpp b/coding/mmap_reader.cpp
index f5c3b23201..84c86aaf42 100644
--- a/coding/mmap_reader.cpp
+++ b/coding/mmap_reader.cpp
@@ -20,13 +20,8 @@ using namespace std;
 
 class MmapReader::MmapData
 {
-  int m_fd;
-
 public:
-  uint8_t * m_memory;
-  uint64_t m_size;
-
-  explicit MmapData(string const & fileName)
+  explicit MmapData(string const & fileName, Advise advise)
   {
     // @TODO add windows support
 #ifndef OMIM_OS_WINDOWS
@@ -40,12 +35,23 @@ public:
     m_size = s.st_size;
 
     m_memory = static_cast<uint8_t *>(
-        mmap(0, static_cast<size_t>(m_size), PROT_READ, MAP_SHARED, m_fd, 0));
+        mmap(0, static_cast<size_t>(m_size), PROT_READ, MAP_PRIVATE, m_fd, 0));
     if (m_memory == MAP_FAILED)
     {
       close(m_fd);
       MYTHROW(OpenException, ("mmap failed for file", fileName));
     }
+
+    int adv = MADV_NORMAL;
+    switch (advise)
+    {
+    case Advise::Random: adv = MADV_RANDOM; break;
+    case Advise::Sequential: adv = MADV_SEQUENTIAL; break;
+    case Advise::Normal: adv = MADV_NORMAL; break;
+    }
+
+    if (madvise(m_memory, s.st_size, adv) != 0)
+      LOG(LWARNING, ("madvise error:", strerror(errno)));
 #endif
   }
 
@@ -57,13 +63,20 @@ public:
     close(m_fd);
 #endif
   }
+
+  uint8_t * m_memory = nullptr;
+  uint64_t m_size = 0;
+
+private:
+  int m_fd = 0;
 };
 
-MmapReader::MmapReader(string const & fileName)
-  : base_type(fileName), m_offset(0)
+MmapReader::MmapReader(string const & fileName, Advise advise)
+  : base_type(fileName)
+  , m_data(std::make_shared<MmapData>(fileName, advise))
+  , m_offset(0)
+  , m_size(m_data->m_size)
 {
-  m_data = shared_ptr<MmapData>(new MmapData(fileName));
-  m_size = m_data->m_size;
 }
 
 MmapReader::MmapReader(MmapReader const & reader, uint64_t offset, uint64_t size)
diff --git a/coding/mmap_reader.hpp b/coding/mmap_reader.hpp
index 1203d01b46..5d0d31a65f 100644
--- a/coding/mmap_reader.hpp
+++ b/coding/mmap_reader.hpp
@@ -11,7 +11,14 @@
 class MmapReader : public ModelReader
 {
 public:
-  explicit MmapReader(std::string const & fileName);
+  enum class Advise
+  {
+    Normal,
+    Random,
+    Sequential
+  };
+
+  explicit MmapReader(std::string const & fileName, Advise advise = Advise::Normal);
 
   uint64_t Size() const override;
   void Read(uint64_t pos, void * p, size_t size) const override;
diff --git a/generator/intermediate_data.cpp b/generator/intermediate_data.cpp
index 9e3717a51c..61252d7ae4 100644
--- a/generator/intermediate_data.cpp
+++ b/generator/intermediate_data.cpp
@@ -75,8 +75,8 @@ private:
 class RawFilePointStorageMmapReader : public PointStorageReaderInterface
 {
 public:
-  explicit RawFilePointStorageMmapReader(string const & name) :
-    m_mmapReader(name)
+  explicit RawFilePointStorageMmapReader(string const & name)
+    : m_mmapReader(name, MmapReader::Advise::Random)
   {}
 
   // PointStorageReaderInterface overrides:
-- 
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