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Merged
yingsu00 merged 1 commit into from
Jul 5, 2024
Merged

Improve the documentation for two memory counters #23126

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21 changes: 10 additions & 11 deletions presto-docs/src/main/sphinx/presto_cpp/properties.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -109,31 +109,30 @@ The configuration properties of Presto C++ workers are described here, in alphab
* **Type:** ``integer``
* **Default value:** ``38``

The total memory capacity that can be used across all query executions.
Memory for system usage such as disk spilling and cache prefetch which
are not counted in query memory usage.
Specifies the total amount of memory in GB that can be used for all queries on a
worker node. Memory for system usage such as disk spilling and cache prefetch are
not counted in it.

``query-reserved-memory-gb``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* **Type:** ``integer``
* **Default value:** ``4``

Specifies the amount of query memory capacity reserved
to ensure that each query has the minimal memory capacity to run. A query can
only allocate from the reserved query memory if its current capacity is less
than the minimal memory capacity as specified by
``memory-pool-reserved-capacity``.

The exceeding capacity must allocate from the non-reserved query memory.
Specifies the total amount of memory in GB reserved for the queries on
a worker node. A query can only allocate from this reserved space if
1) the non-reserved space in ``query-memory-gb`` is used up; and 2) the amount
it tries to get is less than ``memory-pool-reserved-capacity``.

``system-memory-gb``
^^^^^^^^^^^^^^^^^^^^

* **Type:** ``integer``
* **Default value:** ``40``

Memory allocation limit enforced via internal memory allocator.
Memory allocation limit enforced via internal memory allocator. It consists of two parts:
1) Memory used by the queries as specified in ``query-memory-gb``; 2) Memory used by the
system, such as disk spilling and cache prefetch.

Set ``system-memory-gb`` to the available machine memory of the deployment.

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26 changes: 14 additions & 12 deletions presto-native-execution/presto_cpp/main/common/Configs.h
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Expand Up @@ -255,21 +255,21 @@ class SystemConfig : public ConfigBase {

/// Indicates if the process is configured as a sidecar.
static constexpr std::string_view kNativeSidecar{"native-sidecar"};
/// Specifies the total memory capacity that can be used by query execution in
/// GB. The query memory capacity should be configured less than the system
/// memory capacity ('system-memory-gb') to reserve memory for system usage
/// such as disk spilling and cache prefetch which are not counted in query
/// memory usage.

/// Specifies the total amount of memory in GB that the queries can use on a
/// single worker node. It should be configured to be less than the total
/// system memory capacity ('system-memory-gb') such that there is enough room
/// left for the system (as opposed to for the queries), such as disk spilling
/// and cache prefetch.
///
/// NOTE: the query memory capacity is enforced by memory arbitrator so that
/// this config only applies if the memory arbitration has been enabled.
static constexpr std::string_view kQueryMemoryGb{"query-memory-gb"};

/// Specifies the amount of query memory capacity reserved to ensure that each
/// query has minimal memory capacity to run. A query can only allocate from
/// the reserved query memory if its current capacity is less than the minimal
/// memory capacity as specified by 'memory-pool-reserved-capacity'. The
/// exceeding capacity has to allocate from the non-reserved query memory.
/// Specifies the total amount of memory in GB reserved for the queries on
/// a single worker node. A query can only allocate from this reserved space
/// if 1) the non-reserved space in "query-memory-gb" is used up; and 2) the
/// amount it tries to get is less than 'memory-pool-reserved-capacity'.
///
/// NOTE: the reserved query memory capacity is enforced by memory arbitrator
/// so that this config only applies if the memory arbitration has been
Expand Down Expand Up @@ -375,8 +375,10 @@ class SystemConfig : public ConfigBase {
static constexpr std::string_view kMemoryPoolInitCapacity{
"memory-pool-init-capacity"};

/// The minimal amount of memory capacity in bytes reserved for each query
/// memory pool.
/// The amount of memory in bytes reserved for each query memory pool. When
/// a query tries to allocate memory from the reserved space whose size is
/// specified by 'query-reserved-memory-gb', it cannot allocate more than the
/// value specified in 'memory-pool-reserved-capacity'.
static constexpr std::string_view kMemoryPoolReservedCapacity{
"memory-pool-reserved-capacity"};

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