[v7,1/5] docs/migration: add qatzip compression feature

From: Yuan Liu <yuan1.liu@intel.com>

add Intel QATzip compression method introduction

Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
Reviewed-by: Nanhai Zou <nanhai.zou@intel.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Yichen Wang <yichen.wang@bytedance.com>
---
 docs/devel/migration/features.rst           |   1 +
 docs/devel/migration/qatzip-compression.rst | 165 ++++++++++++++++++++
 2 files changed, 166 insertions(+)
 create mode 100644 docs/devel/migration/qatzip-compression.rst

Yichen Wang <yichen.wang@bytedance.com> writes:

> From: Yuan Liu <yuan1.liu@intel.com>
>
> add Intel QATzip compression method introduction
>
> Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
> Reviewed-by: Nanhai Zou <nanhai.zou@intel.com>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Reviewed-by: Yichen Wang <yichen.wang@bytedance.com>
> ---
>  docs/devel/migration/features.rst           |   1 +
>  docs/devel/migration/qatzip-compression.rst | 165 ++++++++++++++++++++
>  2 files changed, 166 insertions(+)
>  create mode 100644 docs/devel/migration/qatzip-compression.rst
>
> diff --git a/docs/devel/migration/features.rst b/docs/devel/migration/features.rst
> index 58f8fd9e16..8f431d52f9 100644
> --- a/docs/devel/migration/features.rst
> +++ b/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
> diff --git a/docs/devel/migration/qatzip-compression.rst b/docs/devel/migration/qatzip-compression.rst
> new file mode 100644
> index 0000000000..a7f755eb7f
> --- /dev/null
> +++ b/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 user space library, to provide extended accelerated compression and
> +decompression services.

"user space library" seems to be duplicated in this sentence.

> +
> +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 Queires

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 Intel 4th Gen Intel Xeon Scalable processors, codenamed Sapphire
> +Rapids processor(``SPR``), it supports multiple build-in accelerators including
> +``QAT`` and ``IAA``, the former can accelerate ``QATzip``, and the latter is
> +used to accelerate ``QPL``.

This sentence needs some work. "Intel" seems to be duplicated, unless
there's a comma somewhere in there to define the subject of the sentence
("it supports"). s/build-in/built-in/ and the last comma before the
"and" can be dropped.

> +
> +Here are some suggestions:
> +
> +1 - If your live migration scenario is limited network bandwidth and ``QAT``
> +hardware resources exceed ``IAA``, then use the ``QATzip`` method, which
> +can save a lot of host CPU resources for compression.
> +
> +2 - If your system cannot support shared virtual memory(SVM) technology, please
> +use ``QATzip`` method because ``QPL`` performance is not good without SVM
> +support.
> +
> +3 - For other scenarios, please use the ``QPL`` method first.

These would be better without the possessives: "If the live migration",
"If the system". Also, this is a nitpick, but "please" doesn't really
fit a technical document.