()

NAME

pmreorder - performs a persistent consistency check using a store reordering mechanism

SYNOPSIS

    $ python pmreorder <options>

DESCRIPTION

The pmreorder tool is a collection of python scripts designed to parse and replay operations logged by pmemcheck - a persistent memory checking tool.

Pmreorder performs the store reordering between persistent memory barriers - a sequence of flush-fence operations. It uses a consistency checking routine provided in the command line options to check whether files are in a consistent state. To help with this task, pmreorder sets an environmental variable PMREORDER_MARKERS. Said variable contains a subset of markers passed from the application, which is visible at the current state of pmreordering. Individual markers are separated by vertical bar (`|').

Example of how PMREORDER_MARKERS variable can be parsed in c++ using regex based environment variable tokener:

        auto env = std::getenv("ENV_PASS");
        std::string senv(env ? env : "");
        std::regex rgx("(\\w+)(\\||$)");
        for (std::sregex_iterator it(senv.begin(), senv.end(), rgx), it_end;
             it != it_end; ++it) {
            std::cout << (*it)[1].str() << std::endl;
        }

Considering that logging, replaying and reordering of operations are very time consuming, it is recommended to use as few stores as possible in test workloads.

OPTIONS

-h, --help

Prints synopsis and list of options.

-l, --logfile <store_log>

The pmemcheck log file to process.

-c, --checker <prog|lib>

Consistency checker type.

-p, --path <path>

Path to the consistency checker. If the checker type is prog - given program has to take a file name as the last parameter and the program has to return 0 for consistent cases and 1 otherwise. If the checker type is lib - --name parameter is required.

-n, --name <name>

The symbol name of the consistency checking function in the library. The function has to take a file name as the only parameter and it has to return 0 for consistent cases and 1 otherwise. This parameter is required only if the checker type is lib.

-o, --output <pmreorder_output>

Set the logger output file.

-e, --output-level <debug|info|warning|error|critical>

Set the output log level.

-r, --default-engine <NoReorderNoCheck | NoReorderDoCheck | ReorderFull | ReorderPartial | ReorderAccumulative | ReorderReverseAccumulative>

Set the initial reorder engine. Default value is NoReorderNoCheck.

-x, --extended-macros <cli_macros|config_file>

Assign an engine types to the defined marker.

-v, --version

Prints current version of pmreorder.

ENGINES

By default, the NoReorderNoCheck engine is used, which means that for each set of stores, the tool will pass-through all sequences of stores not reordered and will not run consistency checker on them.

To enable different types of the reorder engine and begin proper reordering tests, a number of other engines exist:

•   NoReorderDoCheck - pass-through of unchanged operations. Checks correctness of the stores as they were logged. Useful for operations that do not require fail safety.

    Example:
            input: (a, b, c)
            output: (a, b, c)

•   ReorderAccumulative - checks correctness on a growing subset of the original sequence.

    Example:
            input: (a, b, c)
            output:
                   ()
                   (a)
                   (a, b)
                   (a, b, c)

•   ReorderReverseAccumulative - checks correctness on a reverted growing subset of the original sequence.

    Example:
            input: (a, b, c)
            output:
                   ()
                   (c)
                   (c, b)
                   (c, b, a)

•   ReorderPartial - checks consistency on 3 randomly selected sequences from a set of 1000 combinations of the original log, without repetitions.

     Example:
             input: (a, b, c)
             output:
                    (b, c)
                    (b)
                    (a, b, c)

•   ReorderFull - for each set of stores generates and checks consistency of all possible store permutations. This might prove to be very computationally expensive for most workloads. It can be useful for critical sections of code with limited number of stores.

     Example:
            input: (a, b, c)
            output:
                   ()
                   (a)
                   (b)
                   (c)
                   (a, b)
                   (a, c)
                   (b, a)
                   (b, c)
                   (c, a)
                   (c, b)
                   (a, b, c)
                   (a, c, b)
                   (b, a, c)
                   (b, c, a)
                   (c, a, b)
                   (c, b, a)

When the engine is passed with an -r option, it will be used for each logged set of stores. Additionally, the -x parameter can be used to switch engines separately for any marked code sections. For more details about -x extended macros functionality see section INSTRUMENTATION below.

INSTRUMENTATION

The core of pmreorder is based on user-provided named markers. Sections of code can be `marked' depending on their importance, and the degree of reordering can be customized by the use of various provided engines.

For this purpose, Valgrind’s pmemcheck tool exposes a generic marker macro:

•   VALGRIND_PMC_EMIT_LOG(value)

It emits log to store_log during pmemcheck processing. value is a user-defined marker name. For more details about pmemcheck execution see PMEMCHECK STORE LOG section below.

Example:

    main.c
    .
    .
    .
    VALGRIND_PMC_EMIT_LOG("PMREORDER_MEMSET_PERSIST.BEGIN");
    pmem_memset_persist(...);
    VALGRIND_PMC_EMIT_LOG("PMREORDER_MEMSET_PERSIST.END");
    .
    .
    .

There are a few rules for macros creation:

•   Valid macro can have any name, but begin and end section have to match - they are case sensitive.

•   Macro must have .BEGIN or .END suffix.

•   Macros can’t be crossed.

Defined markers can be assigned engines types and configured through the pmreorder tool using the -x parameter.

There are two ways to set macro options:

•   Using command line interface in format:

    PMREORDER_MARKER_NAME1=Marker1,PMREORDER_MARKER_NAME2=Marker2

•   Using configuration file in .json format:

    {
        "PMREORDER_MARKER_NAME1":"Marker1",
        "PMREORDER_MARKER_NAME2":"Marker2"
    }

For more details about available engines types, see ENGINES section above.

libpmemobj(7), libpmem(7) and libpmem2(7) also provide set of macros that allow to change reordering engine on library or function level:

<library_name|api_function_name>

Example of configuration on function level:

    {
        "pmemobj_open":"NoReorderNoCheck",
        "pmemobj_memcpy_persist":"ReorderPartial"
    }

Example of configuration on library level (affecting all library functions):

    {
        "libpmemobj":"NoReorderNoCheck"
    }

List of marked libpmemobj(7) API functions:

    pmemobj_alloc
    pmemobj_cancel
    pmemobj_check
    pmemobj_close
    pmemobj_create
    pmemobj_ctl_exec
    pmemobj_ctl_set
    pmemobj_free
    pmemobj_list_insert
    pmemobj_list_insert_new
    pmemobj_list_move
    pmemobj_list_remove
    pmemobj_memcpy
    pmemobj_memmove
    pmemobj_memset
    pmemobj_memcpy_persist
    pmemobj_memset_persist
    pmemobj_open
    pmemobj_publish
    pmemobj_realloc
    pmemobj_reserve
    pmemobj_root
    pmemobj_root_construct
    pmemobj_strdup
    pmemobj_tx_abort
    pmemobj_tx_add_range
    pmemobj_tx_add_range_direct
    pmemobj_tx_alloc
    pmemobj_tx_commit
    pmemobj_tx_free
    pmemobj_tx_publish
    pmemobj_tx_realloc
    pmemobj_tx_strdup
    pmemobj_tx_wcsdup
    pmemobj_tx_xadd_range
    pmemobj_tx_xadd_range_direct
    pmemobj_tx_xalloc
    pmemobj_tx_zalloc
    pmemobj_tx_zrealloc
    pmemobj_wcsdup
    pmemobj_xalloc
    pmemobj_xreserve
    pmemobj_zalloc
    pmemobj_zrealloc

List of marked libpmem(7) API functions:

    pmem_memmove
    pmem_memcpy
    pmem_memset
    pmem_memmove_nodrain
    pmem_memcpy_nodrain
    pmem_memset_nodrain
    pmem_memmove_persist
    pmem_memcpy_persist
    pmem_memset_persist

List of libpmem2(7) API functions, which return marked functions:

    pmem2_get_memcpy_fn (marker for the returned function has "pmem2_memmove" name)
    pmem2_get_memmove_fn (marker for the returned function has "pmem2_memmove" name)
    pmem2_get_memset_fn (marker for the returned function has "pmem2_memset" name)

PMEMCHECK STORE LOG

To generate store_log for pmreorder run pmemcheck with additional parameters:

    valgrind \
        --tool=pmemcheck \
        -q \
        --log-stores=yes \
        --print-summary=no \
        --log-file=store_log.log \
        --log-stores-stacktraces=yes \
        --log-stores-stacktraces-depth=2 \
        --expect-fence-after-clflush=yes \
        test_binary writer_parameter

For further details of pmemcheck parameters see pmemcheck documentation (https://pmem.io/valgrind/generated/pmc-manual.html)

ENVIRONMENT

By default all logging from PMDK libraries is disabled. To enable API macros logging set environment variable:

•   PMREORDER_EMIT_LOG=1

User defined markers passed from an application are stored in the variable:

•   PMREORDER_MARKERS

EXAMPLE

    python pmreorder.py \
            -l store_log.log \
            -r NoReorderDoCheck \
            -o pmreorder_out.log \
            -c prog \
            -x PMREORDER_MARKER_NAME=ReorderPartial \
            -p checker_binary checker_parameter(s)

Checker binary will be used to run consistency checks on “store_log.log”, output of pmemcheck tool. Any inconsistent stores found during pmreorder analysis will be logged to pmreorder_out.log.

SEE ALSO

<https://pmem.io>