Concept RAM Disk Acceleration

Concept: RAM-Disk Shared Memory Acceleration

Turkce Dokumantasyon | English Documentation

Category: Core Concepts & Architecture
Subsystem: Cache & Buffer Engine (AmberDB::Cache)
Entry Type: Architectural Concept

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1. Definition and Overview

RAM-Disk Shared Memory Acceleration is AmberDB's architecture for achieving sub-microsecond in-memory table read/write latencies by mounting an OS-level shared memory filesystem (tmpfs on Linux or ImDisk on Windows) under dbstore/cache/.

Because AmberDB uses raw Berkeley DB (DB_File) hash files, caching is not restricted to a single Perl worker process. All parallel worker processes (e.g. Plack/Starman/Apache mod_perl workers) access the same shared memory mapped table files concurrently using kernel-managed page caching and non-blocking shared OS flock locks.

RAM-Disk Multi-Process Shared Memory Architecture
  
 Perl Worker Process 1       Perl Worker Process 2       Perl Worker Process N     
  
                                                                        
              
                                      
             Shared RAM-Disk Filesystem (/dev/shm or ImDisk R:)
             dbstore/cache/catalog_category.db & .inx (In-Memory Hash)
                                      
                                       Atomic Preload ($adb->cache_preload)
                                      
             Persistent Physical Storage Disk (dbstore/tables/*.db)

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2. Table Cache Configurations (use_cache)

In the table schema (schema/*.table):

• use_cache => 0: Standard disk-backed reads/writes.
• use_cache => 1: Direct memory caching on read operations with TTL expiration check (cache_ttl => 3600).
• use_cache => 2: Strict RAM-Disk Mirroring. AmberDB automatically ensures the entire table is preloaded into RAM-disk on first access via cache_ensure(). All subsequent read operations run purely against the RAM-disk.

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3. Practical Code Example

# Check RAM-disk mount status and environment diagnostics
my $diag = $adb->cache_setup();
print "RAM-Disk Mounted: $diag->{is_mounted} (Size: $diag->{cache_size})\n";

# Atomically preload a high-traffic table (e.g. categories) into memory
$adb->cache_preload("catalog_category");

# Read from memory cache (sub-microsecond response time)
my @category = $adb->cache_read("catalog_category", 12);

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4. See Also

• Method: cache_setup
• Method: cache_read
• Method: cache_preload
• Method: cache_ensure
• File: .cache (RAM Cache File)