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https://issues.apache.org/jira/browse/IGNITE-12096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16914311#comment-16914311
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Denis Magda commented on IGNITE-12096:
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I'm not sure that the recommended way for the used space calculation. Memory
cleaning can be deferred until the compaction process kicks off:
https://apacheignite.readme.io/docs/memory-defragmentation
Try to adjust the way you do the calculation and see if there is any change:
https://apacheignite.readme.io/docs/memory-metrics#section-memory-usage-calculation
But I still believe that we need to way for next compaction round to purge
deleted entries from memory. [~DmitriyGovorukhin] does it sound correct?
> Ignite memory metrics incorrect on cache usage contraction
> ----------------------------------------------------------
>
> Key: IGNITE-12096
> URL: https://issues.apache.org/jira/browse/IGNITE-12096
> Project: Ignite
> Issue Type: Bug
> Components: cache
> Affects Versions: 2.7
> Reporter: Colin Cassidy
> Priority: Critical
>
> When using the Ignite metrics API to measure available memory, the usage
> figures appear to be accurate while memory is being consumed - but when
> memory is freed the metrics do not drop. They appear to report that memory
> has not been freed up, even though it has.
> Reproducer below. This affects Ignite 2.7+.
> {{}}{{import org.apache.ignite.failure.NoOpFailureHandler; }}
> {{import org.junit.Test; }}
> {{public class MemoryTest2 { }}
> {{ private static final String CACHE_NAME = "cache"; }}
> {{ private static final String DEFAULT_MEMORY_REGION = "Default_Region"; }}
> {{ private static final long MEM_SIZE = 100L * 1024 * 1024; }}
> {{ @Test }}
> {{ public void testOOM() throws InterruptedException { }}
> {{ try (Ignite ignite = startIgnite("IgniteMemoryMonitorTest1")) { }}
> {{ fillDataRegion(ignite); }}
> {{ CacheConfiguration<Object, Object> cfg = new }}
> {{CacheConfiguration<>(CACHE_NAME); }}
> {{ cfg.setStatisticsEnabled(true); }}
> {{ IgniteCache<Object, Object> cache = }}
> {{ignite.getOrCreateCache(cfg); }}
> {{ // Clear all entries from the cache to free up memory }}
> {{ memUsed(ignite); }}
> {{ cache.clear(); }}
> {{ cache.removeAll(); }}
> {{ cache.put("Key", "Value"); }}
> {{ memUsed(ignite); }}
> {{ cache.destroy(); }}
> {{ Thread.sleep(5000); }}
> {{ // Should now report close to 0% but reports 59% still }}
> {{ memUsed(ignite); }}
> {{ } }}
> {{ } }}
> {{ }}
> {{ private Ignite startIgnite(String instanceName) { }}
> {{ IgniteConfiguration cfg = new IgniteConfiguration(); }}
> {{ cfg.setIgniteInstanceName(instanceName); }}
> {{ cfg.setDataStorageConfiguration(createDataStorageConfiguration());
> }}
> {{ cfg.setFailureHandler(new NoOpFailureHandler()); }}
> {{ return Ignition.start(cfg); }}
> {{ } }}
> {{ private DataStorageConfiguration createDataStorageConfiguration() { }}
> {{ return new DataStorageConfiguration() }}
> {{ .setDefaultDataRegionConfiguration( }}
> {{ new DataRegionConfiguration() }}
> {{ .setName(DEFAULT_MEMORY_REGION) }}
> {{ .setInitialSize(MEM_SIZE) }}
> {{ .setMaxSize(MEM_SIZE) }}
> {{ .setMetricsEnabled(true)); }}
> {{ } }}
> {{ private void fillDataRegion(Ignite ignite) { }}
> {{ byte[] megabyte = new byte[1024 * 1024]; }}
> {{ IgniteCache<Object, Object> cache = }}
> {{ ignite.getOrCreateCache(CACHE_NAME); }}
> {{ for (int i = 0; i < 50; i++) { }}
> {{ cache.put(i, megabyte); }}
> {{ memUsed(ignite); }}
> {{ } }}
> {{ } }}
> {{ private void memUsed(Ignite ignite) { }}
> {{ DataRegionConfiguration defaultDataRegionCfg = }}
> {{ignite.configuration() }}
> {{ .getDataStorageConfiguration() }}
> {{ .getDefaultDataRegionConfiguration(); }}
> {{ String regionName = defaultDataRegionCfg.getName(); }}
> {{ DataRegionMetrics metrics = ignite.dataRegionMetrics(regionName); }}
> {{ float usedMem = metrics.getPagesFillFactor() * }}
> {{metrics.getTotalAllocatedPages() * metrics.getPageSize(); }}
> {{ float pctUsed = 100 * usedMem / defaultDataRegionCfg.getMaxSize();
> }}
> {{ System.out.println("Memory used: " + pctUsed + "%"); }}
> {{ } }}
> {{} }}
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