pmreorder version 1.5

The PMDK repository on GitHub is the ultimate source of information on PMDK from release 2.0! For all questions and to submit eventual issues please follow to that repository. The PMDK documentation collected here should be valid up to the 1.13.1 release but is maintained only on a best-effort basis and may not reflect the latest state of the art.

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
ENGINES
INSTRUMENTATION
PMEMCHECK STORE LOG
ENVIRONMENT
EXAMPLE
SEE ALSO

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

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

The contents of this web site and the associated GitHub repositories are BSD-licensed open source.