Ivan Rakov created IGNITE-12510:
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Summary: In-memory page eviction may fail in case very large
entries are stored in the cache
Key: IGNITE-12510
URL: https://issues.apache.org/jira/browse/IGNITE-12510
Project: Ignite
Issue Type: Bug
Affects Versions: 2.7.6
Reporter: Ivan Rakov
In-memory page eviction (both DataPageEvictionMode#RANDOM_LRU and
DataPageEvictionMode#RANDOM_2_LRU) has limited number of attempts to choose
candidate page for data removal:
{code:java}
if (sampleSpinCnt > SAMPLE_SPIN_LIMIT) { // 5000
LT.warn(log, "Too many attempts to choose data page: " +
SAMPLE_SPIN_LIMIT);
return;
}
{code}
Large data entries are stored in several data pages which are sequentially
linked to each other. Only "head" pages are suitable for eviction, because the
whole entry is available only from "head" page (list of pages is singly linked;
there are no reverse links from tail to head).
The problem is that if we put large enough entries to evictable cache (e.g.
each entry needs more than 5000 pages to be stored), there are too few head
pages and "Too many attempts to choose data page" error is likely to show up.
We need to perform something like full scan if we failed to find a head page in
SAMPLE_SPIN_LIMIT attempts instead of just failing node with error.
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