Intel® QuickAssist Technology ZSTD Plugin (QAT ZSTD Plugin)

Table of Contents

• Introduction
• Licensing
• Hardware Requirements
• Software Requirements
• Limitations
• Installation Instructions
• Legal

Introduction

Intel® QuickAssist Technology ZSTD Plugin (QAT ZSTD Plugin) is a plugin to Zstandard*(ZSTD*) for accelerating compression by QAT. ZSTD* is a fast lossless compression algorithm, targeting real-time compression scenarios at zlib-level and better compression ratios. ZSTD* provides block-level sequence producer API which allows users to register their custom sequence producer that libzstd invokes to process each block from 1.5.4. The produced list of sequences (literals and matches) is then post-processed by libzstd to produce valid compressed blocks.

Intel® QuickAssist Technology (Intel® QAT) provides cryptographic and compression acceleration capabilities used to improve performance and efficiency across the data center. QAT sequence producer will offload the process of producing block-level sequences of L1-L12 compression to Intel® QAT, and get performance gain.

Licensing

The Licensing of the files within this project is split as follows:

Intel® QuickAssist Technology ZSTD Plugin - BSD License. Please see the LICENSE file contained in the top level folder. Further details can be found in the file headers of the relevant files.

Hardware Requirements

Intel® 4xxx (Intel® QuickAssist Technology Gen 4)

Software Requirements

ZSTD* library of version 1.5.4+

public ZSTD-lib

Intel® QAT Driver for Linux* Hardware v2.0 or Intel® QuickAssist Technology Library (QATlib) of version 22.07.0+

Limitations

1. Supports compression levels L1 to L12
2. ZSTD* sequence producer only supports ZSTD* compression API which respects advanced parameters, such as ZSTD_compress2, ZSTD_compressStream2.
3. The ZSTD_c_enableLongDistanceMatching cParam is not currently supported. Compression will fail if it is enabled and tries to compress with QAT sequence producer.
4. Dictionaries are not currently supported. Compression will succeed if the dictionary is referenced, but the dictionary will have no effect.
5. Stream history is not currently supported. All advanced ZSTD* compression APIs, including streaming APIs, work with QAT sequence producer, but each block is treated as an independent chunk without history from previous blocks.
6. Multi-threading within a single compression is not currently supported. In other words, compression will fail if ZSTD_c_nbWorkers > 0 and an external sequence producer is registered. Each thread must have its own context (CCtx).

For more details about ZSTD* sequence producer, please refer to zstd.h.

Installation Instructions

Build and install Intel® QuickAssist Technology Driver

Users can choose Intel® QAT Driver for Linux* Hardware v2.0(out-of-tree) or Intel® QuickAssist Technology Library (QATlib)(in-tree) according to their requirements.

If using out-of-tree driver, the user needs to set ICP_ROOT environment variable:

ICP_ROOT: the root directory of the QAT driver source tree

Build and install Intel® QAT Driver for Linux* Hardware v2.0

Download from Intel® QAT Driver for Linux* Hardware v2.0, follow the guidance: Intel® QuickAssist Technology Software for Linux* - Getting Started Guide.

If installing the Intel® QAT 2.0 driver for use in a virtual environment, please refer to Using Intel® Virtualization Technology (Intel® VT) with Intel® QuickAssist Technology

After installing the QAT driver, please refer to Intel® QuickAssist Technology Software for Linux* - Programmer's Guide to the update QAT configuration file according to requirements.

QAT ZSTD Plugin needs a [SHIM] section by default. There are two ways to change:

• QAT driver default conf file does not contain a [SHIM] section which the QAT ZSTD Plugin requires by default. You can add a [SHIM] section for QAT ZSTD Plugin.
• The default section name in the QAT ZSTD Plugin can be modified if required by setting the environment variable "QAT_SECTION_NAME".

After updating the configuration files, please restart QAT.

    service qat_service restart

Install QATlib

QATlib has been upstream to some platforms, RedHat, SUSE. Users also can install QATlib from source code according to qatlib/INSTALL.

Build QAT sequence producer library

Before build, set the QATlib environment variables to prevent compilation errors.

export LIBRARY_PATH=/usr/local/lib
export LD_LIBRARY_PATH=/usr/local/lib

Shared Virtual Memory (SVM) allows direct submission of an application buffer, thus removing the memcpy cycle cost, cache thrashing, and memory bandwidth. The SVM feature enables passing virtual addresses to the QAT hardware for processing acceleration requests.

QAT sequence producer library runs on the SVM environment by default.

To enable SVM, please refer to Using Intel® Virtualization Technology (Intel® VT) with Intel® QuickAssist Technology to update the BIOS and Intel® QuickAssist Technology Software for Linux* - Programmer's Guide to update driver configuration.

    make

If ZSTD* 1.5.4 library is not installed, need to specify path to ZSTD* lib source root by compile variable "ZSTDLIB".

    make ZSTDLIB=[PATH TO ZSTD LIB SOURCE]

USDM support

If SVM is not enabled, memory passed to Intel® QuickAssist Technology hardware must be DMA enabled.

Intel provides a User Space DMA-able Memory (USDM) component (kernel driver and corresponding user space library) which allocates/frees DMA-able memory, mapped to user space, performs virtual to physical address translation on memory allocated by this library. Please refer to Intel® QuickAssist Technology Software for Linux* - Programmer's Guide.

QAT ZSTD Plugin will automatically switch to USDM mode when SVM is not enabled.

Build and run test program

    make test
    ./test/test [TEST FILENAME]

Build and run benchmark tool

The benchmark is a tool used to perform QAT sequence producer performance tests, it supports the following options:

    -t#       Set maximum threads [1 - 128] (default: 1)
    -l#       Set iteration loops [1 - 1000000](default: 1)
    -c#       Set chunk size (default: 32K)
    -E#       Auto/enable/disable searchForExternalRepcodes(0: auto; 1: enable; 2: disable; default: auto)
    -L#       Set compression level [1 - 12] (default: 1)
    -m#       Benchmark mode, 0: software compression; 1:QAT compression(default: 1)

In order to get a better performance, increasing the number of threads with -t is a better way. The number of dc instances provided by Intel® QAT needs to be increased while increasing test threads, it can be increased by modifying the NumberDcInstances in /etc/4xxx_devx.conf. Note that the test threads number should not exceed the number of dc instances, as this ensures that each test thread can obtain a dc instance. For more Intel® QAT configuration information, please refer to Intel® QuickAssist Technology Software for Linux* - Programmer's Guide. An example usage of benchmark tool with Silesia compression corpus:

Silesia is standard lossless data compression corpora.

   ./benchmark -m1 -l100 -c64K -t64 -E2 Silesia

which used the following Intel® QAT configuration file:

    # QAT configuration file /etc/4xxx_devx.conf
    ##############################################
    # User Process Instance Section
    ##############################################
    [SHIM]
    NumberCyInstances = 0
    NumberDcInstances = 64
    NumProcesses = 1
    LimitDevAccess = 0

    # Data Compression - User instance #0
    Dc1Name = "Dc0"
    Dc1IsPolled = 1
    # List of core affinities
    Dc1CoreAffinity = 0

    # Data Compression - User instance #1
    Dc2Name = "Dc1"
    Dc2IsPolled = 1
    # List of core affinities
    Dc2CoreAffinity = 1
    ...
    # Data Compression - User instance #63
    Dc63Name = "Dc63"
    Dc63IsPolled = 1
    # List of core affinities
    Dc63CoreAffinity = 63

How to integrate QAT sequence producer into zstd

Integrating QAT sequence producer into the zstd command can speed up its compression, The following sample code shows how to enable QAT sequence producer by modifying the code of FIO_compressZstdFrame in zstd/programs/fileio.c, including qatseqprod.h in fileio.c and adding -lqatseqprod into Makefile.

Start QAT device and register qatSequenceProducer before starting compression job.

    /* Start QAT device, start QAT device at any
    time before compression job started */
    QZSTD_startQatDevice();
    /* Create sequence producer state for QAT sequence producer */
    void *sequenceProducerState = QZSTD_createSeqProdState();
    /* register qatSequenceProducer */
    ZSTD_registerSequenceProducer(
        ress.cctx,
        sequenceProducerState,
        qatSequenceProducer
    );
    /* Enable sequence producer fallback */
    ZSTD_CCtx_setParameter(ress.cctx, ZSTD_c_enableSeqProducerFallback, 1);

Stop QAT device after compression job

    /* Free sequence producer state */
    QZSTD_freeSeqProdState(sequenceProducerState);
    /* Please call QZSTD_stopQatDevice before
    QAT is no longer used or the process exits */
    QZSTD_stopQatDevice();

Then recompile zstd with flag -lqatseqprod. Currently, only single-threaded mode compression is supported to using QAT sequence producer, please run zstd with the --single-thread.

Note : some parameters of zstd do not support sequence producer, for more zstd usage information please refer to zstd manual.

    ./zstd --single-thread [TEST FILENAME]

How to integrate QAT sequence producer into applications

Initialization

Start and initialize the QAT device.

Create sequence producer state for QAT sequence producer, then call ZSTD_registerSequenceProducer to register it in the application source code.

    ZSTD_CCtx* const zc = ZSTD_createCCtx();
    /* Start QAT device, start QAT device at any
    time before compression job started */
    QZSTD_startQatDevice();
    /* Create sequence producer state for QAT sequence producer */
    void *sequenceProducerState = QZSTD_createSeqProdState();
    /* register qatSequenceProducer */
    ZSTD_registerSequenceProducer(
        zc,
        sequenceProducerState,
        qatSequenceProducer
    );
    /* Enable sequence producer fallback */
    ZSTD_CCtx_setParameter(zc, ZSTD_c_enableSeqProducerFallback, 1);

Compression API

No changes to the application with calling ZSTD* compression API, keep calling ZSTD_compress2, ZSTD_compressStream2, or ZSTD_compressStream to compress.

    /* Compress */
    ZSTD_compress2(zc, dstBuffer, dstBufferSize, srcBuffer, srcbufferSize);

Free resources and shutdown QAT device

    /* Free sequence producer state */
    QZSTD_freeSeqProdState(sequenceProducerState);
    /* Please call QZSTD_stopQatDevice before
    QAT is no longer used or the process exits */
    QZSTD_stopQatDevice();

Then link to libzstd and libqatseqprod like test program did. See the DEMO in test/test.c file

Legal

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