docs/migration: add qatzip compression feature

add Intel QATzip compression method introduction

Reviewed-by: Nanhai Zou <nanhai.zou@intel.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
Signed-off-by: Yichen Wang <yichen.wang@bytedance.com>
Link: https://lore.kernel.org/r/20240830232722.58272-2-yichen.wang@bytedance.com
Signed-off-by: Peter Xu <peterx@redhat.com>

docs/devel/migration/features.rst

@@ -14,3 +14,4 @@ Migration has plenty of features to support different use cases.
    CPR
    qpl-compression
    uadk-compression
+   qatzip-compression

docs/devel/migration/qatzip-compression.rst

@@ -0,0 +1,165 @@
+==================
+QATzip Compression
+==================
+In scenarios with limited network bandwidth, the ``QATzip`` solution can help
+users save a lot of host CPU resources by accelerating compression and
+decompression through the Intel QuickAssist Technology(``QAT``) hardware.
+
+
+The following test was conducted using 8 multifd channels and 10Gbps network
+bandwidth. The results show that, compared to zstd, ``QATzip`` significantly
+saves CPU resources on the sender and reduces migration time. Compared to the
+uncompressed solution, ``QATzip`` greatly improves the dirty page processing
+capability, indicated by the Pages per Second metric, and also reduces the
+total migration time.
+
+::
+
+   VM Configuration: 16 vCPU and 64G memory
+   VM Workload: all vCPUs are idle and 54G memory is filled with Silesia data.
+   QAT Devices: 4
+   |-----------|--------|---------|----------|----------|------|------|
+   |8 Channels |Total   |down     |throughput|pages per | send | recv |
+   |           |time(ms)|time(ms) |(mbps)    |second    | cpu %| cpu% |
+   |-----------|--------|---------|----------|----------|------|------|
+   |qatzip     |   16630|       28|     10467|   2940235|   160|   360|
+   |-----------|--------|---------|----------|----------|------|------|
+   |zstd       |   20165|       24|      8579|   2391465|   810|   340|
+   |-----------|--------|---------|----------|----------|------|------|
+   |none       |   46063|       40|     10848|    330240|    45|    85|
+   |-----------|--------|---------|----------|----------|------|------|
+
+
+QATzip Compression Framework
+============================
+
+``QATzip`` is a user space library which builds on top of the Intel QuickAssist
+Technology to provide extended accelerated compression and decompression
+services.
+
+For more ``QATzip`` introduction, please refer to `QATzip Introduction
+<https://github.com/intel/QATzip?tab=readme-ov-file#introductionl>`_
+
+::
+
+  +----------------+
+  | MultiFd Thread |
+  +-------+--------+
+          |
+          | compress/decompress
+  +-------+--------+
+  | QATzip library |
+  +-------+--------+
+          |
+  +-------+--------+
+  |  QAT library   |
+  +-------+--------+
+          |         user space
+  --------+---------------------
+          |         kernel space
+   +------+-------+
+   |  QAT  Driver |
+   +------+-------+
+          |
+   +------+-------+
+   | QAT Devices  |
+   +--------------+
+
+
+QATzip Installation
+-------------------
+
+The ``QATzip`` installation package has been integrated into some Linux
+distributions and can be installed directly. For example, the Ubuntu Server
+24.04 LTS system can be installed using below command
+
+.. code-block:: shell
+
+   #apt search qatzip
+   libqatzip-dev/noble 1.2.0-0ubuntu3 amd64
+     Intel QuickAssist user space library development files
+
+   libqatzip3/noble 1.2.0-0ubuntu3 amd64
+     Intel QuickAssist user space library
+
+   qatzip/noble,now 1.2.0-0ubuntu3 amd64 [installed]
+     Compression user-space tool for Intel QuickAssist Technology
+
+   #sudo apt install libqatzip-dev libqatzip3 qatzip
+
+If your system does not support the ``QATzip`` installation package, you can
+use the source code to build and install, please refer to `QATzip source code installation
+<https://github.com/intel/QATzip?tab=readme-ov-file#build-intel-quickassist-technology-driver>`_
+
+QAT Hardware Deployment
+-----------------------
+
+``QAT`` supports physical functions(PFs) and virtual functions(VFs) for
+deployment, and users can configure ``QAT`` resources for migration according
+to actual needs. For more details about ``QAT`` deployment, please refer to
+`Intel QuickAssist Technology Documentation
+<https://intel.github.io/quickassist/index.html>`_
+
+For more ``QAT`` hardware introduction, please refer to `intel-quick-assist-technology-overview
+<https://www.intel.com/content/www/us/en/architecture-and-technology/intel-quick-assist-technology-overview.html>`_
+
+How To Use QATzip Compression
+=============================
+
+1 - Install ``QATzip`` library
+
+2 - Build ``QEMU`` with ``--enable-qatzip`` parameter
+
+  E.g. configure --target-list=x86_64-softmmu --enable-kvm ``--enable-qatzip``
+
+3 - Set ``migrate_set_parameter multifd-compression qatzip``
+
+4 - Set ``migrate_set_parameter multifd-qatzip-level comp_level``, the default
+comp_level value is 1, and it supports levels from 1 to 9
+
+QAT Memory Requirements
+=======================
+
+The user needs to reserve system memory for the QAT memory management to
+allocate DMA memory. The size of the reserved system memory depends on the
+number of devices used for migration and the number of multifd channels.
+
+Because memory usage depends on QAT configuration, please refer to `QAT Memory
+Driver Queries
+<https://intel.github.io/quickassist/PG/infrastructure_debugability.html?highlight=memory>`_
+for memory usage calculation.
+
+.. list-table:: An example of a PF used for migration
+  :header-rows: 1
+
+  * - Number of channels
+    - Sender memory usage
+    - Receiver memory usage
+  * - 2
+    - 10M
+    - 10M
+  * - 4
+    - 12M
+    - 14M
+  * - 8
+    - 16M
+    - 20M
+
+How To Choose Between QATzip and QPL
+====================================
+Starting from 4th Gen Intel Xeon Scalable processors, codenamed Sapphire Rapids
+processor(``SPR``), multiple built-in accelerators are supported including
+``QAT`` and ``IAA``.  The former can accelerate ``QATzip`` and the latter is
+used to accelerate ``QPL``.
+
+Here are some suggestions:
+
+1 - If the live migration scenario is limited by network bandwidth and ``QAT``
+hardware resources exceed ``IAA``, use the ``QATzip`` method, which can save a
+lot of host CPU resources for compression.
+
+2 - If the system cannot support shared virtual memory (SVM) technology, use
+the ``QATzip`` method because ``QPL`` performance is not good without SVM
+support.
+
+3 - For other scenarios, use the ``QPL`` method first.