Redis Latency spikes when used as a LRU cache

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Anuj Mittal

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Jun 21, 2015, 1:39:45 PM6/21/15
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Hi,

I am using redis 2.8.13 as a LRU cache, with persistence disabled. I have given 80GB maxmemory to redis and it is running on a bare metal . At certain frequency redis get latency shoots upto 2-3 seconds, key sizes being from few KBs to 4-5 MBs.
Any reason why that sort of behavior is consistently happening?
Let me know if you need more details. 
These are the memory stats
# Memory
used_memory:85898932040
used_memory_human:80.00G
used_memory_rss:96645287936
used_memory_peak:85911130704
used_memory_peak_human:80.01G
used_memory_lua:33792
mem_fragmentation_ratio:1.13
mem_allocator:jemalloc-3.6.0

Josiah Carlson

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Jun 22, 2015, 12:19:29 AM6/22/15
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Do you have a large number of keys that expire at roughly the same time? Either explicitly by using EXPIREAT, or as an accidental "the app fills the cache when it can't find the cache key", so a large amount of data gets cycled in and out at times corresponding to when the application started using Redis and a given expiration?

Can you provide us with more (all) of your INFO output? Have you checked the SLOWLOG? Do you have slaves? Do you observe them disconnecting periodically?

 - Josiah

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