Record a garbage collection and analysis of gceasy

background

Recently, the system always appears younggc Too many times , The time point is not unified , Take it GC Frequent GC journal , use GCeasy Look at the .

GCEasy brief introduction

gceasy It's a very good GClog Analysis tools , It's online , Free analysis , You can upload related gc Log for online analysis ：https://gceasy.io/gc-index.jsp#banner

GCEasy Practical analysis

1. GC Memory analysis ：
   
   Here is JVM Memory allocation , It means that the younger generation has been allocated 2.41gb Peak time allocation 2.4gb
   Old age Already allocated 3.8gb Peak value 751.6mb, Total memory size

2. Key performance indicators
Mainly throughput （ The proportion of normal business execution time , In fact, roughly speaking , Namely 1- subtract GC Of time ）、 Delay time （GC Pause time ） form , The exhibition shows an average 、 Maximum delay time and at GC During logging , Proportion of different pause time .
In general , We GC The purpose of tuning , Is to improve throughput , Reduce GC Average pause time （ Reduce the maximum , Reduce the number of times ）.

3. GC Interactive view
   This is this time period GC Comprehensive analysis curve of , Respectively GC The next pile 、GC Previous heap ,GC Time for 、 Number of bytes recycled 、 The younger generation 、 Old age 、 Distribution vs. promotion 、 Object tenure summary .
   The first two are no longer expanded , Namely GC The size of the front and back stacks .

Let's take a look at GC Duration：GC Duration of , This is more interesting （ Select a part to zoom in ）, The points in this figure actually cover the parallel time gc Time and stop the world Time for , It's total gc Time .

GC Number of bytes reclaimed ：
The selected part can still be enlarged , And a dot represents one gc Size of recycled bytes , It can be seen that 10：22-10：24gc Quite frequently , But the recovery efficiency is also low , It will be found later that the reason is this moment , The allocation space of the young generation is very small .

Young generation size ：
Allocated space and gc The size of the front and back , It can be seen that the allocated space is 22-23 The score is very small , And all GC The front is covered with ,GC Later, it was recycled .

Old generation size ：
ditto , Illustrates the 22-23 Of the young generation are assigned to the era , Nearly 3.8g, But the old generation does not occupy much , Need to observe the reason .

Distribution and promotion
According to the figure below , Promotion has not been very high .

Expected survivor zone size And Actual survivor area size ：
This is actually related to a parameter we configured ：：-XX:TargetSurvivorRatio （ Set up survivor The target usage of the zone ）
desired survivor size = (survivor Area capacity * TargetSurvivorRatio)/100（ In fact, that is survivor Multiply the capacity by this targetSurvivorRatio The ratio of the ） If you are interested, you can continue to see , Here I will not introduce more .

4.GC Statistics

I won't explain it one by one here ：
The three pictures above ： Number of bytes reclaimed 、GC Time for 、GC The average time , It can be seen that there is no fullgc（ This heel G1 The characteristics of garbage collector ）.
The following is GC The statistics of ： The total GC frequency 、 Total bytes reclaimed 、 The total GC Time 、gc average time ...
5.GC Statistics of pause information

6. Object statistics
The total size of the created object 、 Total promotion size 、 The rate of both .
It can be seen that the creation rate of this object is still quite high , Need to optimize .

7. Memory leak 、fullgc、 Long pause

8. Safe point duration ：
The safety point here actually refers to stop the world The timing of the , The time here actually refers to stop the world The total time of .

9.GC cause

10. Object tenure summary

summary

It's on it GCEasy The general analysis report , From this report , In fact, some problems have been found , For example, the rate of memory allocation 、 The total number of bytes allocated in memory is very high , It indicates that you need to optimize the number of objects created or the size of objects .
At a special point in time , I found that the young generation suddenly became very small , This time period will cause frequent younggc, It needs to be carefully analyzed further according to the business scenario , Why at that time GC The older generation allocates a lot of memory .
I hope this article can help you , I also hope to have a discussion with you .