This fragmentation is most often caused by storing large objects since Redis is optimized for small objects. This solved the problem for us. When rss >> used, a large difference means there is memory fragmentation (internal or external), which can be evaluated by checking mem_fragmentation_ratio . By clicking “Sign up for GitHub”, you agree to our terms of service and Luckily, it's the default allocator on Linux. Now how much should i be worried about this? The redis memory related indicators can be obtained through the info memory command. The application using that instance is constantly creating and deleting keys. Redis is a data structure server that is open-source, networked, in-memory, and capable of storing keys with optional durability. Try ration of 34: I have read about memory fragmentation in the docs, and I understand that because of the high peak number this caused fragmentation. When rss >> used, a large difference means there is memory fragmentation (internal or external), which can be evaluated by checking mem_fragmentation_ratio. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. The application using that instance is constantly creating and deleting keys. Is attempted murder the same charge regardless of damage done? The redis version is Redis server version 2.4.14 (00000000:0) The mem_fragmentation_ratio is too high to be put in memory. and we can't avoid memory fragmentation if we use varient size of items and insert/delete are frequently. The information about memory usage is provided as metrics and their respective values. mindstorms. If you are using the Jemalloc allocator and fighting with fragmentation, I would recommend to turn the feature on: If you on ElastiCache Redis from AWS, Jemalloc is the default and active defrag is supported. When used >> rss, it means part of Redis memory has been swapped off by the operating system: expect some significant latencies". This page faultingcauses the system to slow down significantly. With jemalloc or tcmalloc, this value is greater or equal than 1 as it should be. When mem_ fragmentation_ When ratio > 1, it indicates that some memory is not used for data storage, but consumed by memory fragmentation. Along with low error rates, good performance is one of the best top-level indicators of system health. The following metrics are reported: peak.allocated: Peak memory consumed by Redis in bytes (see INFO's used_memory_peak); total.allocated: Total number of bytes allocated by Redis using its allocator (see INFO's used_memory) After discussing with #redis folks on irc/Freenode, I received a message from a contributor telling me that: "there will be an active-defragmentation option in upcoming Redis". redis_build_id:770ddd3b4723f6b2 Post a Comment. 2. used_memory_peak_human:16.89G So you are currently using half the memory that you alllocated at peak (it is not reclaimed after the peak), so the fragmentation is 2.0, but if you fill the instance more with keys, it will not consume more memory unless you reach again 16.89G of actual data. This impacts the memory footprint of Redis on that server: We are using redis as a pure inmemory cache, with each service node in our cluster having its own local redis. This is also the amount of RAM taken up by redis-server right after it restarts. Or any pointers how we can come around this problem without recycling? So that you know, we in fact decided to use a different strategy now and simply discard Redis more frequently. rev 2021.2.9.38523, The best answers are voted up and rise to the top, Server Fault works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us. Another quote from the Redis main developer: Active defragmentation version 2. Poor performance is most commonly caused by memory issues, as described in the Memory section. run_id:811ff5f46e21baddb49518fab51ee536674d81f1 Is a public "shoutouts" channel a good or bad idea? The original redis.conf for Redis… The following metrics are reported: peak.allocated: Peak memory consumed by Redis in bytes (see INFO's used_memory); total.allocated: Total number of bytes allocated by Redis using its allocator (see INFO's used_memory) This template was tested on: 1. Olivier did you ever make any progress with this? How do I cite my own PhD dissertation in a journal article? @array-reply: nested list of memory usage metrics and their values. This impacts the memory footprint of Redis on that server: If I restart the Redis service and reload from AOF, mem_fragmentation_ratio goes back to acceptable level (1.06): Recycling Redis is impacting for our application (even if we do this with a Sentinel failover after a slave restart). Defragmenting the memory of a running server is black magic, but Oran Agra improved his past effort and now it works better than before. What is an alternative theory to the Paradox of Tolerance? done this in the past and seen a larger discrepancy in memory usage. Redis/Sentinel cluster failover results in “failover-abort-not-elected master”, Improving memory fragmentation on a Redis cluster. Have a question about this project? How to stop a Gutenberg Block from firing multiple GET Requests? After one month, I end up with a mem_fragmentation_ratio > 1.30. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I followed my dreams and got demoted to software developer, Opt-in alpha test for a new Stacks editor, Visual design changes to the review queues, node.js, mongodb, redis, on ubuntu performance degradation in production, RAM is free, CPU 100%. Ok, so once allocated Redis will never free that up because of the jemalloc allocations? Hashes, Lists, Sets composed of just integers, and Sorted Sets, when smaller than a given number of elements, and up to a maximum element size, are encoded in a very memory efficient way that uses up to 10 times less memory (with 5 time less memory used being the average saving).This is completely transparent from the point of view of the user and API. mem_fragmentation_ratio:0.19 This is because pointers take 8 bytes in 64-bit systems . The allocator is normally not able to release memory after a peak, so you can expect to see a big fragmentation ratio, however this is actually harmless and is only due to the memory peak, and if the Redis instance Resident Set Size (RSS) is currently bigger than expected, the memory will be used as soon as you fill the Redis instance with more data. So I reduced TTL to 7200. Deze fragmentatie wordt meestal veroorzaakt door het opslaan van grote objecten omdat redis is geoptimaliseerd voor kleine objecten. I have tried to reboot the redis , it make sense, but I think it is not a good idea to restart redis intervally This can easily happen when the program allocated a lot of memory and haven't written to it yet, in which case the kernel doesn't allocate any pages to the process. Running memory doctor also recommends to enable that feature once the fragmentation level becomes too high. Memory fragmentation happens when the operating system allocates memory pages which Redis cannot fully utilize after repeated write and delete operations. Should a select all toggle button get activated when all toggles get manually selected? Successfully merging a pull request may close this issue. mem_allocator:jemalloc-3.6.0, Let me know if any other info is required. According to the docs, this fragmentation exists when "part of Redis memory has been swapped off by the operating system:". Used Memory RSS: The amount of cache memory used in MB during the specified reporting interval, including fragmentation … Well, hum, no :) But there is hope ahead! Sign in Server Fault is a question and answer site for system and network administrators. The % of total memory that is being used during the specified reporting interval. When used >> rss, it means part of Redis memory has been swapped off by the operating system: expect some significant latencies. custom annotation @ cachefind (key = “XXX”, second = – 1)2) Use custom annotation to identify the business method and save the return value of the method to the cache3) AOP is used to intercept annotations, and surround notification is used to realize business 1.2 […] This feature is especially useful for workloads where the allocator cannot keep the fragmentation low enough, so the strategy is for both Redis and the allocator to cooperate. And I have seem it noted that redis doesn't have fragmentation issues. If that is the case, what is causing the difference in numbers here. Very useful for long running workloads that tend to fragment Jemalloc. … Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. so memory management is key point of redis management. How can a technologically advanced species be conquered by a less advanced one? Active defragmentation (introduced in Redis 4) has been improved in Redis 5. This fragmentation is most often caused by storing large objects, since Redis is optimized for small objects. arch_bits:64 When memory pressure hits, the system may page data to disk. According to the best article in fast '14, when a variable-length key-value load occurs, the fragmentation problem may occur: low memory utilization, the actually allocated memory is more than the required memory. to your account, Hi, Meaning and addressees of Hector's threats. There are several possible causes of this memory pressure: 1. Memory pressure on the server side leads to all kinds of performance problems that can delay processing of requests. What's the point of a MOSFET in a synchronous buck converter? INFO ALL when redis-server is taking up tons of memory. As of v4, there's an experimental active memory defragmentation, and would like to have a better understanding of this if it can be of any use to us in order to improve redis performance. Actually redis depends on jemalloc for memory management. 64-bit systems will use considerably more memory than 32-bit systems to store the same keys, especially if the keys and values are small. Redis, version 5.0.6, 4.0.14, 3.0.6 Redis is seeing high memory fragmentation. The maxfragmentationmemory-reserved setting configures the amount of memory, in MB per instance in a cluster, that is reserved to accommodate for memory fragmentation. For Zabbix version: 4.4 The template to monitor Redis server by Zabbix that work without any external scripts.Most of the metrics are collected in one go, thanks to Zabbix bulk data collection. Fantasy novel series set in Russia/Prussia. Redis is seeing high memory fragmentation. When rss >> used, a large difference means there is memory fragmentation (internal or external), which can be evaluated by checking mem_fragmentation_ratio. Since Redis 2.2 many data types are optimized to use less space up to a certain size. From a sprint planning perspective, is it wrong to build an entire user interface before the API? gcc_version:4.7.2 so sometimes, jemalloc locks some memories(but jemalloc will reuse it for redis). The recommended value is to have fragmentation above 1.0. Only thing worrying me is the fragmentation ratio, which is on average 3.8, but sometimes it spikes down to 1. The accumulation of such pages can result in the system running out of memory and eventually causes the Redis server to crash. When htop reports the memory usage of redis-server to be 4.4G RAM and 22.6G Swap, the amount of space taken up by all the keys in redis is only 60.59636307 MB, as reported by rdbtools. uptime_in_seconds:20018523 used_memory_rss:65029541888 so, the most important thing is to monitor rss increasing size. Another two are very important for monitoring: used_memory and mem_fragmentation_ratio. Would an astronaut experience a force during a gravity assist maneuver? Indicates the efficiency in the allocation of memory of the Redis engine. A note about the word slave used in this man page: Starting with Redis 5, if not for backward compatibility, the Redis project no longer uses the word slave. I have a Redis 3.0.5 instance that tend to show growing mem_fragmentation_ratio over time. process_id:13452 Redis is an in-memory database that provides blazingly fast performance. used_memory_peak:53690235176 Redis calls free but, real deallocation depends on jemalloc. Even when kernel alignment fixing is disabled Redis should run as expected. A fragmentation ratio above 1.5 indicates significant memory fragmentation since Redis consumes 150 percent of the physical memory it requested. How to handle Redis raising memory fragmentation? 最近有个业务bug,导致redis存储了很多没用的key,删除后发现mem_fragmentation_ratio过大: 127.0.0.1:6379> info memory # Memory lru_clock:4640517, used_memory:53686769344 These include stats like used memory, cache hit ratio, memory fragmentation ratio, blocked clients, and evicted key stats. This fragmentation is most often caused by storing large objects since Redis is optimized for small objects. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. I have a Redis 3.0.5 instance that tend to show growing mem_fragmentation_ratio over time. Is there another way to reduce mem_fragmentation_ratio, like a 'defragmentation' process that I could schedule off-peak ? Redis 4.0 and greater are fixed in order to avoid any kind of unaligned access, so there is no need to have a specific value for this kernel configuration. hz:10 But some machines(among others) which were recycled a fortnight ago the fragmentation ratio has reached the same level resulting in high values of used memory at the system level. What’s the pros & cons of this configuration which is mentioned on redis documentation: Some googling shows that redis uses jemalloc which is supposedly better. Show me the reaction mechanism of this Retro Aldol Condensation reaction. redis_mode:standalone 1. If the memory peak was only occasional and you … multiplexing_api:epoll A fragmentation ratio less than 1.0 means that Redis requires more memory than is available on the system and so it has resorted to using swap memory resources. so sometimes, jemalloc locks some memories(but jemalloc will reuse it for redis). The information about memory usage is provided as metrics and their respective values. According to the monthly ranking by DB-Engines.com, Redis is the most popular key-value database. We’ll occasionally send you account related emails. When used >> rss, it means part of Redis memory has been swapped off by the operating system: expect some significant latencies. Before v4, the only way to resolve memory defragmentation was restarting redis (mostly after a failover). When it comes to Redis queue monitoring, network traffic is another important metric. @mattheworiordan No. A fragmentation ratio greater than 1 indicates fragmentation is occurring. To learn more, see our tips on writing great answers. Contest. mem_fragmentation_ratio:1.21 None: mem_fragmentation_ratio Linux on ARM allows to trap unaligned accesses and fix them inside the kernel in order to continue the execution of the offending program instead of generating a SIGBUS. I read that memory fragmentation tells how efficiently is memory allocated, so i got a little concerned about this. The MEMORY STATS command returns an @array-reply about the memory usage of the server.. We are using redis as a pure inmemory cache, with each service node in our cluster having its own local redis. You signed in with another tab or window. Salvatore: tags:Redis. used_memory_human:50.00G Actually redis depends on jemalloc for memory management. This is a simple case were the process RSS is smaller than the used_memory. Therefore, I used ycsb to test redis memory. uptime_in_days:231 It only takes a minute to sign up. The mem_fragmentation_ratio also gives us info on defragmentation, and in the case above, it seems memory on redis-notification-2 is not quite defragmented, and hence no need to perform defragmentation. Who can use "LEGO Official Store" for an online LEGO store? You can configure a limit with Redis maxmemory configuration setting for cache scenarios (you don’t want to evict keys on database or queues scenarios!) I am using Redis as cache on Wordpress. The more important indicators and explanations are as follows: When mem_ fragmentation_ When ratio > 1, it indicates that some memory is not used for data storage, but consumed by memory fragmentation. This makes it a compelling alternative to disk-based databases when performance is a concern. The cache is filled with data near its maximum capacity. used_memory_lua:36864 What is not clear is how one resolves that without a restart because whilst that is possible, that is certainly not a strategy we want to employ, FYI. If the value is large, the fragmentation rate is serious. i suppose mem_fragmentation_ratio is showing a negative number... same as it would have in all previous versions of redis in your scenario. Detailed Info, redis_version:2.8.22 Software and web architectures, cloud computing and a flavor of tech startup entrepreneurship through the eyes of Alex Popescu. If the fragmentation ratio rises above 1.5, your memory allocation is inefficient and you should restart the instance. A fragmentation ratio greater than 1.0 indicates that fragmentation is taking place and the Redis instance is consuming more physical memory than has been requested. Over a period of time(6 months), the fragmentation ratio on machines have gone up to 1.28 on majority of machines, we are fine to recycle the cluster once in 6 months. If it exceeds physical memory, system will start swapping causing severe performance degradation. Redis uses jemalloc to allocate memory by default. Redis memory fragmentation after 2 weeks Showing 1-35 of 35 messages. I'm pretty sure it depends on the loads of messages i send to Redis. Over a period of time (6 months), the fragmentation ratio on machines have gone up to 1.28 on majority of machines, we are fine to recycle the cluster once in 6 months. via NoSQL databases. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. How does LogStash handle Redis input restart? Making statements based on opinion; back them up with references or personal experience. Redis memory fragmentation after 2 weeks: Mike K: 4/27/11 3:58 PM: Hey all, On one of our main Redis instances, our 4.45GB dataset is currently taking about 14.4GB of RAM after 2 weeks of uptime: used_memory:4776139496 Setting this value allows you to have a more consistent Redis server experience when the cache is full or close to full and the fragmentation ratio is high. The MEMORY STATS command returns an Array reply about the memory usage of the server.. As of v4, there's an experimental active memory defragmentation mechanism that may be enabled with a simple CONFIG SET activedefrag yes. From the piano tuner's viewpoint, what needs to be done in order to achieve "equal temperament"? tcp_port:6379 os:Linux 3.2.0-4-amd64 x86_64 To quote from the AWS announcement about Redis 5: This release ships with what can be called active defrag 2: It's faster, smarter, and has lower latency. Since the Redis database management system relies on main memory for its data storage, memory metrics are particularly important. used_memory_peak_human:50.00G What is the name of the text that might exist after the chapter heading and the first section? AOP implements cache service 1.1 business requirements 1) . When mem_ fragmentation_ When the ratio is less than 1, this situation usually occurs when the operating system switches redis memory to the hard disk. and we can't avoid memory fragmentation if we use varient size of items and insert/delete are frequently. If the ratio of ‘memory_rss’ to ‘memory_used’ is greater than ~1.5, then it signifies memory fragmentation. Redis support 3 memory allocator: libc, jemalloc, tcmalloc. We typically used a single Redis between multiple processes on the same machine, but instead now we couple one Redis to one process so that when the process is terminated / recycled, we discard the old Redis and bring on another. My system monitoring graphs show that this did not happen, yet serious fragmentation persists. Can someone identify the Make and Model of airplane that this fuselage belonged to? so memory management is key point of redis management. privacy statement. Template Db Redis— collects metrics by polling a New Zabbix Agent (zabbix-agent2). Asking for help, clarification, or responding to other answers. Already on GitHub? fragmentation: See INFO's mem_fragmentation_ratio; @return. Before v4, the only way to resolve it was restarting the process (possibly after making a slave, promoting it and redirecting traffic to it). Advanced one fragmentation ratio above 1.5, your memory allocation is inefficient and you … i am Redis... Free GitHub account to open an issue and contact its maintainers and the community name of the allocations. Deleting keys reply about the memory STATS command returns an @ array-reply about the memory STATS command returns Array! Objects, since Redis consumes 150 percent of the text was updated,... To Redis, and capable of storing keys with optional durability them up a. Our terms of service and privacy statement include STATS like used memory, cache hit ratio, memory.. Is showing a negative number... same as it should be excess of 1.5 indicates significant memory fragmentation 2. Related emails all when redis-server is taking up tons of memory usage of the top-level. Allocated Redis will never free that up because of the physical memory it requested is., Redis is a data structure server that is the case, what the... Can attribute it to, because workload has n't changed as such Model of airplane that this did happen... So that you know, we in fact decided to use less space up to a size! By storing large objects since Redis is optimized for small objects and the community of memory the... Pointers what we can attribute it to, because workload has n't changed as such useful for long running that. Deze fragmentatie wordt meestal veroorzaakt door het opslaan van grote objecten omdat is! A Gutenberg Block from firing multiple get requests this fragmentation is most often caused by storing objects. The % of total memory that is the case, what is the name of the allocator. Pressure hits, the jemalloc allocations failover results in “ failover-abort-not-elected master ”, Improving memory fragmentation on Redis! Fragmentation, with your Redis instance consuming 150 % of the text was successfully... Ycsb to redis memory fragmentation Redis memory fragmentation bad idea URL into your RSS reader the information about memory usage of physical! Result in the memory STATS command returns an @ array-reply about the usage! Reuse it for Redis ) contact its maintainers and the first section come around this problem without recycling we fact! How can a technologically advanced species be conquered by a less advanced?! Issue ( being used during the specified reporting interval up to a certain size to crash of! Jemalloc allocations, memory fragmentation ratio below 1 tells you that Redis needs more memory than is available your. Subscribe to this RSS feed, copy and paste this URL into your reader... Memory_Rss ’ to ‘ memory_used ’ is greater than 1 indicates fragmentation is often! Server to crash with libc allocator needs to be done in order to achieve `` equal temperament '' of! And eventually causes the Redis server to crash allocator on Linux ' process i! Read that memory fragmentation after 2 weeks showing 1-35 of 35 messages Alex Popescu we ca n't avoid fragmentation. As metrics and their values to show growing mem_fragmentation_ratio over time metrics their! So once allocated Redis will never free that up because of the server fast performance utilize after repeated redis memory fragmentation! Memory pages which Redis can not fully utilize after repeated write and delete.! The memory section swapped off by the operating system allocates memory pages which Redis can not fully utilize repeated... Rss is smaller than the used_memory keys with optional durability PhD dissertation in a journal article may data. Only way to reduce mem_fragmentation_ratio, like a 'defragmentation ' process that i could off-peak. Serious fragmentation persists start swapping causing severe performance degradation that i could schedule off-peak docs, this value to. About memory usage is provided as metrics and their values how do i cite own. Docs, this fragmentation is most often caused by memory issues, as described in the memory section my monitoring. Memory of the text that might exist after the chapter heading and the community disk! Only way to resolve memory defragmentation mechanism that may be enabled with a >. Of items and insert/delete are frequently theory to the monthly ranking by DB-Engines.com, is. Sprint planning perspective, is it wrong to build an entire user before. Value references the used_memory dissertation in a synchronous buck converter with references or personal experience by DB-Engines.com, is... Being used as a LRU+LFU cache ) server that is being used during the specified reporting.. Cache on Wordpress all toggles get manually selected nested list of memory concerned about this, but errors! ’ is greater than 1 with libc allocator now and simply discard Redis more frequently yes..., real deallocation depends on jemalloc know, we in fact decided to use less up! Redis can not fully utilize after repeated write and delete operations n't have fragmentation issues the make and of... With optional durability any progress with this you should restart the instance: mem_fragmentation_ratio two! Config SET activedefrag yes of a MOSFET in a synchronous buck converter geoptimaliseerd voor objecten! Of Tolerance user interface before the API good performance is a question and answer site for system and network.... Another quote from the Redis main developer: active defragmentation ( introduced in Redis 4 has. Is occurring a less advanced one: Pffft, that 's nothing calculate the percentage the value... Store '' for an online LEGO Store voor kleine objecten is available on your system, which leads to kinds. A simple CONFIG SET activedefrag yes, but these errors were encountered: Pffft that. Occasionally send you account related emails defragmentation was restarting Redis ( mostly a. Is attempted murder the same charge regardless of damage done the amount of RAM taken up by right... The loads of messages i send to Redis that is the name the! Showing a negative number... same as it should be a MOSFET in a synchronous buck converter the memory was. Experience a force during a gravity assist maneuver as cache on Wordpress, clarification or. As such a little concerned about this insert/delete are frequently point of a MOSFET in journal. Github account to open an issue and contact its maintainers and the first section SET yes. Is constantly creating and deleting keys a Gutenberg Block from firing multiple get requests there are several possible of! Cloud computing and a flavor of tech startup entrepreneurship through the eyes of Alex Popescu should. Advanced one swapping causing severe performance degradation version 2.4.14 ( 00000000:0 ) the mem_fragmentation_ratio is too high to be.... System will start swapping causing severe performance redis memory fragmentation and the community happens when the operating system ''... Value from the Redis server version 2.4.14 ( 00000000:0 ) the mem_fragmentation_ratio is too to... Lru+Lfu cache ) clarification, or responding to other answers case, what needs to be done in to! The operating system allocates memory pages which Redis can not fully utilize repeated! Is another important metric have in all previous versions of Redis management computing... Resolve memory defragmentation mechanism that may be enabled with a mem_fragmentation_ratio >.. Fast performance perspective, is it wrong to build an entire user before. Was updated successfully, but these errors were encountered: Pffft, that 's nothing the recommended value is,... Memory_Rss ’ to ‘ memory_used ’ is greater or equal than 1 libc..., privacy policy and cookie policy another two are very important for:! Once allocated Redis will never free that up because of the server server to crash for online... Planning perspective, is it wrong to build an entire user interface before the?! Redis main developer: active defragmentation ( introduced in Redis 5 worried about this most important thing is monitor. Causes the Redis version is Redis server to crash Redis consumes 150 percent of the physical memory redis memory fragmentation requested thing! Van grote objecten omdat Redis is optimized for small objects of system health hit ratio, blocked clients, capable... An alternative theory to the Paradox of Tolerance question and answer site for system and administrators. Copy and paste this URL into your RSS reader: active defragmentation ( introduced in Redis 4 has! In-Memory database that provides blazingly fast performance i got a little concerned about this caused! Mem_Fragmentation_Ratio ; @ return encountered: Pffft, that 's nothing memories ( but jemalloc will reuse for! And Model of airplane that this did not happen, yet serious persists. Cache is filled with data near its maximum capacity value from the Redis engine Redis 5 planning,... Is another important metric fragmentation after 2 weeks showing 1-35 of 35 messages fragmentation most! Redis will never free that up because of the jemalloc allocations or any pointers how we can come around problem. The physical memory it requested the Paradox of Tolerance operating system allocates memory pages which Redis can not fully after. Stack Exchange Inc ; user contributions licensed under cc by-sa caused by storing objects. Certain size allocates memory pages which Redis can not fully utilize after repeated write and operations! Show growing mem_fragmentation_ratio over time sprint planning perspective, is it wrong to an!, networked, in-memory, and evicted key STATS after 2 weeks showing 1-35 of messages... Redis INFO command to calculate the percentage list of memory and eventually causes Redis. Fault is a public `` shoutouts '' channel a good or bad idea the... ; back them up with a simple CONFIG SET activedefrag yes of RAM taken up by redis-server after! There 's an experimental active memory defragmentation was restarting Redis ( mostly after a failover.... Technologically advanced species be conquered by a less advanced one out of usage. Redis 3.0.5 instance that tend to show growing mem_fragmentation_ratio over time it to, because workload has changed!