From 3d5140e66385194cd2f75d346cb4eaf7059947e9 Mon Sep 17 00:00:00 2001
From: Ziye Yang <optimistyzy@gmail.com>
Date: Thu, 31 Aug 2017 14:07:48 +0800
Subject: [PATCH] os/bluestore/NVMEDevice: fix the large write I/O issue.

When there is large I/O, we need to split it into multiple
tasks. With this patch, we can avoid no buffer allocation
issue for the single write task.

Signed-off-by: Ziye Yang <optimistyzy@gmail.com>
Signed-off-by: Pan Liu <wanjun.lp@alibaba-inc.com>
---
 src/os/bluestore/NVMEDevice.cc | 86 ++++++++++++++++++----------------
 1 file changed, 45 insertions(+), 41 deletions(-)

diff --git a/src/os/bluestore/NVMEDevice.cc b/src/os/bluestore/NVMEDevice.cc
index 9141d5b19eb..e72b81e61b0 100644
--- a/src/os/bluestore/NVMEDevice.cc
+++ b/src/os/bluestore/NVMEDevice.cc
@@ -328,11 +328,6 @@ struct Task {
     io_request.nseg = 0;
   }
 
-  void copy_to_buf(const bufferptr& p, uint64_t off, uint64_t len) {
-    copy_to_buf((char *)p.c_str(), off, len);
-    bl.append(std::move(p));
-  }
-
   void copy_to_buf(char *buf, uint64_t off, uint64_t len) {
     uint64_t copied = 0;
     uint64_t left = len;
@@ -983,10 +978,41 @@ void NVMEDevice::aio_submit(IOContext *ioc)
     ioc->num_pending -= pending;
     assert(ioc->num_pending.load() == 0);  // we should be only thread doing this
     // Only need to push the first entry
-  if(queue_id == -1)
-    queue_id = ceph_gettid();
-    driver->get_queue(queue_id)->queue_task(t, pending);
+    if (queue_id == -1)
+      queue_id = ceph_gettid();
     ioc->nvme_task_first = ioc->nvme_task_last = nullptr;
+    driver->get_queue(queue_id)->queue_task(t, pending);
+  }
+}
+
+static void write_split(
+    NVMEDevice *dev,
+    uint64_t off,
+    bufferlist &bl,
+    IOContext *ioc)
+{
+  uint64_t remain_len = bl.length(), begin = 0, write_size;
+  Task *t, *first, *last;
+  // This value may need to be got from configuration later.
+  uint64_t split_size = 131072; // 128KB.
+
+  while (remain_len > 0) {
+    write_size = std::min(remain_len, split_size);
+    t = new Task(dev, IOCommand::WRITE_COMMAND, off + begin, write_size);
+    // TODO: if upper layer alloc memory with known physical address,
+    // we can reduce this copy
+    bl.splice(0, write_size, &t->bl);
+    remain_len -= write_size;
+    t->ctx = ioc;
+    first = static_cast<Task*>(ioc->nvme_task_first);
+    last = static_cast<Task*>(ioc->nvme_task_last);
+    if (last)
+      last->next = t;
+    if (!first)
+      ioc->nvme_task_first = t;
+    ioc->nvme_task_last = t;
+    ++ioc->num_pending;
+    begin += write_size;
   }
 }
 
@@ -1001,22 +1027,7 @@ int NVMEDevice::aio_write(
            << " buffered " << buffered << dendl;
   assert(is_valid_io(off, len));
 
-  Task *t = new Task(this, IOCommand::WRITE_COMMAND, off, len);
-
-  // TODO: if upper layer alloc memory with known physical address,
-  // we can reduce this copy
-  t->bl = std::move(bl);
-
-  t->ctx = ioc;
-  Task *first = static_cast<Task*>(ioc->nvme_task_first);
-  Task *last = static_cast<Task*>(ioc->nvme_task_last);
-  if (last)
-    last->next = t;
-  if (!first)
-    ioc->nvme_task_first = t;
-  ioc->nvme_task_last = t;
-  ++ioc->num_pending;
-
+  write_split(this, off, bl, ioc);
   dout(5) << __func__ << " " << off << "~" << len << dendl;
 
   return 0;
@@ -1034,18 +1045,9 @@ int NVMEDevice::write(uint64_t off, bufferlist &bl, bool buffered)
   assert(off + len <= size);
 
   IOContext ioc(cct, NULL);
-  Task *t = new Task(this, IOCommand::WRITE_COMMAND, off, len);
-
-  // TODO: if upper layer alloc memory with known physical address,
-  // we can reduce this copy
-  t->bl = std::move(bl);
-  t->ctx = &ioc;
-  if(queue_id == -1)
-    queue_id = ceph_gettid();
-  ++ioc.num_running;
-  driver->get_queue(queue_id)->queue_task(t);
-
+  write_split(this, off, bl, &ioc);
   dout(5) << __func__ << " " << off << "~" << len << dendl;
+  aio_submit(&ioc);
   ioc.aio_wait();
   return 0;
 }
@@ -1061,10 +1063,11 @@ int NVMEDevice::read(uint64_t off, uint64_t len, bufferlist *pbl,
   bufferptr p = buffer::create_page_aligned(len);
   int r = 0;
   t->ctx = ioc;
-  pbl->append(std::move(t->bl));
-  t->fill_cb = [p, t]() {
-    t->copy_to_buf(p, 0, t->len);
+  char *buf = p.c_str();
+  t->fill_cb = [buf, t]() {
+    t->copy_to_buf(buf, 0, t->len);
   };
+
   ++ioc->num_running;
   if(queue_id == -1)
     queue_id = ceph_gettid();
@@ -1091,10 +1094,11 @@ int NVMEDevice::aio_read(
   Task *t = new Task(this, IOCommand::READ_COMMAND, off, len);
 
   bufferptr p = buffer::create_page_aligned(len);
-  pbl->append(std::move(t->bl));
+  pbl->append(p);
   t->ctx = ioc;
-  t->fill_cb = [p, t]() {
-    t->copy_to_buf(p, 0, t->len);
+  char* buf = p.c_str();
+  t->fill_cb = [buf, t]() {
+    t->copy_to_buf(buf, 0, t->len);
   };
 
   Task *first = static_cast<Task*>(ioc->nvme_task_first);
-- 
2.39.5