Linux VM Subsystem - File Cache Demonstration #1
I was at work today and came across a performance problem with an internal Java application. Long story short, someone suggested that because the filesystem cache was full we had run out of memory and should drop caches. I suggested that this was a bad idea and said that Linux handled this itself and we need not do that.
But rather than just take my word for it, or the word of people like Mel Gorman, here is a demonstration that I wrote up. I had to spin up a VM in AWS and install perl and CPAN and Linux::MemInfo. After that I wrote up the code which is available at https://github.com/ndietsch/linux-system-programming.
As you can see from the screencast, I created a perl program that creates a 10MB file of zeros and then reads this into a noop loop. With each iteration, you can see the free memory drop by 10MB and the active file cache increase by 10MB. Once the system hits about 9-10MB free, it starts moving the cache from active to inactive and then evicting as necessary. This proves that Linux can handle the cache ejections by itself.
The next installments of this will show how anonymous memory increasing will also shrink the cache. But for now, here is the screencast ... enjoy.
I have included the terminal session below, but also a tar file of scriptreplay files if you want the interactive experience
I have included the terminal session below, but also a tar file of scriptreplay files if you want the interactive experience
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ cat intro; sleep 30
* This screencast is to demonstrate the cache eviction feature of the Linux Virtual Memory Management subsystem.
* In this example, our Perl code creates a 10MB file with DD and then reads it into a loop.
* The loop outputs three figures each time
- MemFree
- Active (File) which makes up the active part of the file cache
- Inactive (File) which makes up the inactive part of the file cache
* As you can see from the /proc/meminfo output, we start with a relatively high amount of free memory on our 1GB system and a low amount of filesystem cache
* With each loop, the free memory decreases by about 10MB and the Active file cache increases by about 10MB.
* Once we hit around 9-11MB free on the system, the VM subsystem automatically moves the cache from active to inactive where it is then evicted using the various algorithms
* Please note that this is using Amazon Linux with Kernel 4.1.17-22.30.amzn1.x86_64 which will differ slightly from the internal Linux systems at ${work} but it demonstrates the point none the less.
* The really cool bit is at the end when we delete all the files
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ cat /proc/meminfo
MemTotal: 1019444 kB
MemFree: 934832 kB
MemAvailable: 969936 kB
Buffers: 1024 kB
Cached: 16828 kB
SwapCached: 0 kB
Active: 22168 kB
Inactive: 9376 kB
Active(anon): 13700 kB
Inactive(anon): 52 kB
Active(file): 8468 kB
Inactive(file): 9324 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 13696 kB
Mapped: 5484 kB
Shmem: 60 kB
Slab: 41288 kB
SReclaimable: 31880 kB
SUnreclaim: 9408 kB
KernelStack: 1408 kB
PageTables: 2356 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 509720 kB
Committed_AS: 62876 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 2488 kB
VmallocChunk: 34359731159 kB
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 22528 kB
DirectMap2M: 1026048 kB
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ cat ActiveFileCache.pl
use strict;
use Linux::MemInfo;
my %mem;
my $count;
# Starting values
%mem = get_mem_info;
printf("%-20s\t%s\n","Active(file)",$mem{"Active(file)"});
printf("%-20s\t%s\n","Active(anon)",$mem{"Active(anon)"});
while() {
sleep 1;
$count++;
# Create a 10MB file full of zeros and then read it to fill the Active(file) cache from /proc/meminfo
my $retval=system("/bin/dd if=/dev/zero of=/tmp/file.${count} count=20480 > /dev/null 2>&1");
open(my $fh, "){}
# Get memory statistics after creating and reading a 5MB file, watch Active(file) grow until it is 5MB
%mem = get_mem_info;
my $time = localtime;
printf("%s\n",$time);
printf("%-20s\t%s\n","Active(file)",$mem{"Active(file)"});
printf("%-20s\t%s\n","Inactive(file)",$mem{"Inactive(file)"});
printf("%-20s\t%s\n\n","MemFree",$mem{"MemFree"});
}
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ perl ActiveFileCache.pl
Active(file) 8508
Active(anon) 14332
Wed Mar 2 06:07:54 2016
Active(file) 18780
Inactive(file) 9284
MemFree 923476
Wed Mar 2 06:07:55 2016
Active(file) 29000
Inactive(file) 9268
MemFree 913068
Wed Mar 2 06:07:56 2016
Active(file) 39276
Inactive(file) 9272
MemFree 902536
Wed Mar 2 06:07:57 2016
Active(file) 49504
Inactive(file) 9272
MemFree 891980
Wed Mar 2 06:07:58 2016
Active(file) 59720
Inactive(file) 9272
MemFree 881572
Wed Mar 2 06:07:59 2016
Active(file) 69984
Inactive(file) 9272
MemFree 871016
Wed Mar 2 06:08:00 2016
Active(file) 80244
Inactive(file) 9272
MemFree 860360
Wed Mar 2 06:08:01 2016
Active(file) 90448
Inactive(file) 9272
MemFree 849952
Wed Mar 2 06:08:02 2016
Active(file) 100712
Inactive(file) 9272
MemFree 839520
Wed Mar 2 06:08:03 2016
Active(file) 110964
Inactive(file) 9272
MemFree 828988
Wed Mar 2 06:08:04 2016
Active(file) 121208
Inactive(file) 9272
MemFree 818548
Wed Mar 2 06:08:05 2016
Active(file) 131428
Inactive(file) 9272
MemFree 808012
Wed Mar 2 06:08:06 2016
Active(file) 141692
Inactive(file) 9272
MemFree 797480
Wed Mar 2 06:08:07 2016
Active(file) 151932
Inactive(file) 9272
MemFree 787020
Wed Mar 2 06:08:08 2016
Active(file) 162160
Inactive(file) 9272
MemFree 776484
Wed Mar 2 06:08:09 2016
Active(file) 172400
Inactive(file) 9272
MemFree 765924
Wed Mar 2 06:08:10 2016
Active(file) 182624
Inactive(file) 9272
MemFree 755392
Wed Mar 2 06:08:12 2016
Active(file) 192888
Inactive(file) 9272
MemFree 744960
Wed Mar 2 06:08:13 2016
Active(file) 203128
Inactive(file) 9272
MemFree 734404
Wed Mar 2 06:08:14 2016
Active(file) 213380
Inactive(file) 9272
MemFree 723996
Wed Mar 2 06:08:15 2016
Active(file) 223620
Inactive(file) 9272
MemFree 713440
Wed Mar 2 06:08:16 2016
Active(file) 233880
Inactive(file) 9272
MemFree 702908
Wed Mar 2 06:08:17 2016
Active(file) 244108
Inactive(file) 9272
MemFree 692476
Wed Mar 2 06:08:18 2016
Active(file) 254360
Inactive(file) 9272
MemFree 681940
Wed Mar 2 06:08:19 2016
Active(file) 264576
Inactive(file) 9272
MemFree 671284
Wed Mar 2 06:08:20 2016
Active(file) 274840
Inactive(file) 9272
MemFree 660884
Wed Mar 2 06:08:21 2016
Active(file) 285052
Inactive(file) 9272
MemFree 650352
Wed Mar 2 06:08:22 2016
Active(file) 295316
Inactive(file) 9272
MemFree 639792
Wed Mar 2 06:08:23 2016
Active(file) 305532
Inactive(file) 9272
MemFree 629384
Wed Mar 2 06:08:24 2016
Active(file) 318796
Inactive(file) 7160
MemFree 617968
Wed Mar 2 06:08:25 2016
Active(file) 329052
Inactive(file) 7152
MemFree 607448
Wed Mar 2 06:08:26 2016
Active(file) 339288
Inactive(file) 7152
MemFree 597016
Wed Mar 2 06:08:27 2016
Active(file) 349528
Inactive(file) 7152
MemFree 586460
Wed Mar 2 06:08:28 2016
Active(file) 359780
Inactive(file) 7152
MemFree 576036
Wed Mar 2 06:08:29 2016
Active(file) 370020
Inactive(file) 7152
MemFree 565536
Wed Mar 2 06:08:30 2016
Active(file) 380272
Inactive(file) 7152
MemFree 555004
Wed Mar 2 06:08:31 2016
Active(file) 390508
Inactive(file) 7152
MemFree 544448
Wed Mar 2 06:08:32 2016
Active(file) 400724
Inactive(file) 7152
MemFree 533916
Wed Mar 2 06:08:33 2016
Active(file) 410988
Inactive(file) 7152
MemFree 523360
Wed Mar 2 06:08:34 2016
Active(file) 421228
Inactive(file) 7156
MemFree 512928
Wed Mar 2 06:08:35 2016
Active(file) 431480
Inactive(file) 7156
MemFree 502396
Wed Mar 2 06:08:36 2016
Active(file) 441716
Inactive(file) 7156
MemFree 491840
Wed Mar 2 06:08:37 2016
Active(file) 451932
Inactive(file) 7156
MemFree 481432
Wed Mar 2 06:08:38 2016
Active(file) 462200
Inactive(file) 7156
MemFree 470904
Wed Mar 2 06:08:39 2016
Active(file) 472424
Inactive(file) 7156
MemFree 460432
Wed Mar 2 06:08:40 2016
Active(file) 482688
Inactive(file) 7156
MemFree 449892
Wed Mar 2 06:08:41 2016
Active(file) 492936
Inactive(file) 7156
MemFree 439476
Wed Mar 2 06:08:42 2016
Active(file) 503176
Inactive(file) 7156
MemFree 428936
Wed Mar 2 06:08:43 2016
Active(file) 513416
Inactive(file) 7156
MemFree 418380
Wed Mar 2 06:08:44 2016
Active(file) 523656
Inactive(file) 7156
MemFree 407856
Wed Mar 2 06:08:46 2016
Active(file) 533896
Inactive(file) 7156
MemFree 397440
Wed Mar 2 06:08:47 2016
Active(file) 544144
Inactive(file) 7156
MemFree 386900
Wed Mar 2 06:08:48 2016
Active(file) 554384
Inactive(file) 7156
MemFree 376484
Wed Mar 2 06:08:49 2016
Active(file) 564624
Inactive(file) 7156
MemFree 365944
Wed Mar 2 06:08:50 2016
Active(file) 574864
Inactive(file) 7156
MemFree 355280
Wed Mar 2 06:08:51 2016
Active(file) 585108
Inactive(file) 7164
MemFree 344864
Wed Mar 2 06:08:52 2016
Active(file) 595356
Inactive(file) 7164
MemFree 334324
Wed Mar 2 06:08:53 2016
Active(file) 605596
Inactive(file) 7164
MemFree 323908
Wed Mar 2 06:08:54 2016
Active(file) 615836
Inactive(file) 7164
MemFree 313368
Wed Mar 2 06:08:55 2016
Active(file) 626076
Inactive(file) 7164
MemFree 302828
Wed Mar 2 06:08:56 2016
Active(file) 636324
Inactive(file) 7156
MemFree 292396
Wed Mar 2 06:08:57 2016
Active(file) 646572
Inactive(file) 7156
MemFree 281840
Wed Mar 2 06:08:58 2016
Active(file) 656812
Inactive(file) 7156
MemFree 271268
Wed Mar 2 06:08:59 2016
Active(file) 667052
Inactive(file) 7156
MemFree 260712
Wed Mar 2 06:09:00 2016
Active(file) 677292
Inactive(file) 7156
MemFree 250140
Wed Mar 2 06:09:01 2016
Active(file) 687532
Inactive(file) 7156
MemFree 239708
Wed Mar 2 06:09:02 2016
Active(file) 697780
Inactive(file) 7156
MemFree 229136
Wed Mar 2 06:09:03 2016
Active(file) 708020
Inactive(file) 7156
MemFree 218704
Wed Mar 2 06:09:04 2016
Active(file) 718260
Inactive(file) 7156
MemFree 208132
Wed Mar 2 06:09:05 2016
Active(file) 728500
Inactive(file) 7156
MemFree 197700
Wed Mar 2 06:09:06 2016
Active(file) 738752
Inactive(file) 7156
MemFree 187128
Wed Mar 2 06:09:07 2016
Active(file) 749000
Inactive(file) 7156
MemFree 176448
Wed Mar 2 06:09:08 2016
Active(file) 759240
Inactive(file) 7156
MemFree 166000
Wed Mar 2 06:09:09 2016
Active(file) 769480
Inactive(file) 7156
MemFree 155444
Wed Mar 2 06:09:10 2016
Active(file) 779720
Inactive(file) 7156
MemFree 145012
Wed Mar 2 06:09:11 2016
Active(file) 789952
Inactive(file) 7160
MemFree 134440
Wed Mar 2 06:09:12 2016
Active(file) 800208
Inactive(file) 7160
MemFree 123884
Wed Mar 2 06:09:13 2016
Active(file) 810448
Inactive(file) 7160
MemFree 113436
Wed Mar 2 06:09:14 2016
Active(file) 820688
Inactive(file) 7160
MemFree 102880
Wed Mar 2 06:09:15 2016
Active(file) 830928
Inactive(file) 7160
MemFree 92308
Wed Mar 2 06:09:16 2016
Active(file) 841180
Inactive(file) 7160
MemFree 81752
Wed Mar 2 06:09:17 2016
Active(file) 851428
Inactive(file) 7160
MemFree 71180
Wed Mar 2 06:09:18 2016
Active(file) 861668
Inactive(file) 7160
MemFree 60748
Wed Mar 2 06:09:20 2016
Active(file) 871908
Inactive(file) 7160
MemFree 50176
Wed Mar 2 06:09:21 2016
Active(file) 882148
Inactive(file) 7160
MemFree 39744
Wed Mar 2 06:09:22 2016
Active(file) 892388
Inactive(file) 7160
MemFree 29172
Wed Mar 2 06:09:23 2016
Active(file) 902636
Inactive(file) 7160
MemFree 18616
^C
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "Once we hit aboit 9MB free, the system will start moving the file data fromt he active cache to the inactive cache. From there it will evict the data, ensuring Linux always has enough free memory for OS and applications"
Once we hit aboit 9MB free, the system will start moving the file data fromt he active cache to the inactive cache. From there it will evict the data, ensuring Linux always has enough free memory for OS and applications
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ perl ActiveFileCache.pl
Active(file) 902680
Active(anon) 14344
Wed Mar 2 06:10:13 2016
Active(file) 902676
Inactive(file) 7164
MemFree 18476
Wed Mar 2 06:10:14 2016
Active(file) 902688
Inactive(file) 7164
MemFree 18480
Wed Mar 2 06:10:15 2016
Active(file) 902652
Inactive(file) 7164
MemFree 18480
Wed Mar 2 06:10:16 2016
Active(file) 902676
Inactive(file) 7164
MemFree 18480
Wed Mar 2 06:10:17 2016
Active(file) 902688
Inactive(file) 7164
MemFree 18480
Wed Mar 2 06:10:18 2016
Active(file) 902688
Inactive(file) 7164
MemFree 18504
Wed Mar 2 06:10:20 2016
Active(file) 902684
Inactive(file) 7164
MemFree 18500
Wed Mar 2 06:10:21 2016
Active(file) 902696
Inactive(file) 7164
MemFree 18500
Wed Mar 2 06:10:22 2016
Active(file) 902708
Inactive(file) 7164
MemFree 18500
Wed Mar 2 06:10:23 2016
Active(file) 902696
Inactive(file) 7164
MemFree 18476
Wed Mar 2 06:10:24 2016
Active(file) 902684
Inactive(file) 7164
MemFree 18500
Wed Mar 2 06:10:25 2016
Active(file) 902716
Inactive(file) 7164
MemFree 18476
Wed Mar 2 06:10:26 2016
Active(file) 902716
Inactive(file) 7164
MemFree 18488
Wed Mar 2 06:10:27 2016
Active(file) 902680
Inactive(file) 7168
MemFree 18484
Wed Mar 2 06:10:28 2016
Active(file) 902692
Inactive(file) 7168
MemFree 18480
Wed Mar 2 06:10:29 2016
Active(file) 902728
Inactive(file) 7168
MemFree 18380
Wed Mar 2 06:10:30 2016
Active(file) 902724
Inactive(file) 7168
MemFree 18480
Wed Mar 2 06:10:31 2016
Active(file) 902712
Inactive(file) 7168
MemFree 18380
Wed Mar 2 06:10:32 2016
Active(file) 902712
Inactive(file) 7168
MemFree 18516
Wed Mar 2 06:10:33 2016
Active(file) 902724
Inactive(file) 7168
MemFree 18376
Wed Mar 2 06:10:34 2016
Active(file) 902736
Inactive(file) 7168
MemFree 18400
Wed Mar 2 06:10:35 2016
Active(file) 902732
Inactive(file) 7168
MemFree 18500
Wed Mar 2 06:10:36 2016
Active(file) 902744
Inactive(file) 7168
MemFree 18376
Wed Mar 2 06:10:37 2016
Active(file) 902708
Inactive(file) 7168
MemFree 18488
Wed Mar 2 06:10:38 2016
Active(file) 902720
Inactive(file) 7168
MemFree 18360
Wed Mar 2 06:10:39 2016
Active(file) 902744
Inactive(file) 7168
MemFree 18484
Wed Mar 2 06:10:40 2016
Active(file) 902716
Inactive(file) 7168
MemFree 18484
^C
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 7.8G 2.2G 5.5G 29% /
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ rm /tmp/file*
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ perl ActiveFileCache.pl
Active(file) 11884
Active(anon) 14368
Wed Mar 2 06:10:52 2016
Active(file) 22096
Inactive(file) 7260
MemFree 921944
Wed Mar 2 06:10:53 2016
Active(file) 32324
Inactive(file) 7260
MemFree 911552
Wed Mar 2 06:10:54 2016
Active(file) 42584
Inactive(file) 7260
MemFree 901100
Wed Mar 2 06:10:55 2016
Active(file) 52812
Inactive(file) 7260
MemFree 890580
Wed Mar 2 06:10:56 2016
Active(file) 63076
Inactive(file) 7260
MemFree 880032
Wed Mar 2 06:10:57 2016
Active(file) 73316
Inactive(file) 7260
MemFree 869600
Wed Mar 2 06:10:58 2016
Active(file) 83568
Inactive(file) 7260
MemFree 859068
Wed Mar 2 06:10:59 2016
Active(file) 93796
Inactive(file) 7260
MemFree 848512
Wed Mar 2 06:11:00 2016
Active(file) 104056
Inactive(file) 7260
MemFree 838052
Wed Mar 2 06:11:02 2016
Active(file) 114284
Inactive(file) 7260
MemFree 827452
Wed Mar 2 06:11:03 2016
Active(file) 124512
Inactive(file) 7260
MemFree 816908
Wed Mar 2 06:11:04 2016
Active(file) 134740
Inactive(file) 7260
MemFree 806500
Wed Mar 2 06:11:05 2016
Active(file) 145004
Inactive(file) 7260
MemFree 795944
Wed Mar 2 06:11:06 2016
Active(file) 155228
Inactive(file) 7260
MemFree 785412
Wed Mar 2 06:11:07 2016
Active(file) 165492
Inactive(file) 7260
MemFree 774980
Wed Mar 2 06:11:08 2016
Active(file) 175744
Inactive(file) 7260
MemFree 764424
Wed Mar 2 06:11:09 2016
Active(file) 185960
Inactive(file) 7260
MemFree 754016
Wed Mar 2 06:11:10 2016
Active(file) 196224
Inactive(file) 7264
MemFree 743464
Wed Mar 2 06:11:11 2016
Active(file) 206484
Inactive(file) 7264
MemFree 733044
Wed Mar 2 06:11:12 2016
Active(file) 216700
Inactive(file) 7264
MemFree 722484
Wed Mar 2 06:11:13 2016
Active(file) 226964
Inactive(file) 7264
MemFree 711960
Wed Mar 2 06:11:14 2016
Active(file) 237192
Inactive(file) 7264
MemFree 701528
Wed Mar 2 06:11:15 2016
Active(file) 247432
Inactive(file) 7264
MemFree 690972
Wed Mar 2 06:11:16 2016
Active(file) 257692
Inactive(file) 7264
MemFree 680440
Wed Mar 2 06:11:17 2016
Active(file) 267920
Inactive(file) 7264
MemFree 670008
Wed Mar 2 06:11:18 2016
Active(file) 278148
Inactive(file) 7264
MemFree 659352
Wed Mar 2 06:11:19 2016
Active(file) 288412
Inactive(file) 7264
MemFree 648920
Wed Mar 2 06:11:20 2016
Active(file) 298652
Inactive(file) 7264
MemFree 638364
Wed Mar 2 06:11:21 2016
Active(file) 308900
Inactive(file) 7264
MemFree 627840
Wed Mar 2 06:11:22 2016
Active(file) 319152
Inactive(file) 7264
MemFree 617424
Wed Mar 2 06:11:23 2016
Active(file) 329356
Inactive(file) 7264
MemFree 606888
Wed Mar 2 06:11:24 2016
Active(file) 339620
Inactive(file) 7264
MemFree 596452
Wed Mar 2 06:11:25 2016
Active(file) 349872
Inactive(file) 7264
MemFree 585920
Wed Mar 2 06:11:26 2016
Active(file) 360108
Inactive(file) 7264
MemFree 575364
Wed Mar 2 06:11:27 2016
Active(file) 370348
Inactive(file) 7264
MemFree 564932
Wed Mar 2 06:11:28 2016
Active(file) 380572
Inactive(file) 7264
MemFree 554400
Wed Mar 2 06:11:29 2016
Active(file) 390828
Inactive(file) 7264
MemFree 543956
Wed Mar 2 06:11:30 2016
Active(file) 401080
Inactive(file) 7264
MemFree 533432
Wed Mar 2 06:11:31 2016
Active(file) 411316
Inactive(file) 7264
MemFree 522900
Wed Mar 2 06:11:32 2016
Active(file) 421556
Inactive(file) 7264
MemFree 512316
Wed Mar 2 06:11:33 2016
Active(file) 431808
Inactive(file) 7264
MemFree 501760
Wed Mar 2 06:11:34 2016
Active(file) 442048
Inactive(file) 7264
MemFree 491328
Wed Mar 2 06:11:36 2016
Active(file) 452300
Inactive(file) 7264
MemFree 480796
Wed Mar 2 06:11:37 2016
Active(file) 462536
Inactive(file) 7264
MemFree 470364
Wed Mar 2 06:11:38 2016
Active(file) 472776
Inactive(file) 7264
MemFree 459792
Wed Mar 2 06:11:39 2016
Active(file) 483028
Inactive(file) 7264
MemFree 449364
Wed Mar 2 06:11:40 2016
Active(file) 493256
Inactive(file) 7264
MemFree 438824
Wed Mar 2 06:11:41 2016
Active(file) 503496
Inactive(file) 7264
MemFree 428284
Wed Mar 2 06:11:42 2016
Active(file) 513744
Inactive(file) 7264
MemFree 417868
Wed Mar 2 06:11:43 2016
Active(file) 523984
Inactive(file) 7264
MemFree 407328
Wed Mar 2 06:11:44 2016
Active(file) 534236
Inactive(file) 7264
MemFree 396788
Wed Mar 2 06:11:45 2016
Active(file) 544476
Inactive(file) 7264
MemFree 386248
Wed Mar 2 06:11:46 2016
Active(file) 554716
Inactive(file) 7264
MemFree 375708
Wed Mar 2 06:11:47 2016
Active(file) 564964
Inactive(file) 7268
MemFree 365292
Wed Mar 2 06:11:48 2016
Active(file) 575204
Inactive(file) 7268
MemFree 354752
Wed Mar 2 06:11:49 2016
Active(file) 585444
Inactive(file) 7268
MemFree 344336
Wed Mar 2 06:11:50 2016
Active(file) 595684
Inactive(file) 7268
MemFree 333796
Wed Mar 2 06:11:51 2016
Active(file) 605924
Inactive(file) 7268
MemFree 323256
Wed Mar 2 06:11:52 2016
Active(file) 616172
Inactive(file) 7268
MemFree 312840
Wed Mar 2 06:11:53 2016
Active(file) 626412
Inactive(file) 7268
MemFree 302176
Wed Mar 2 06:11:54 2016
Active(file) 636664
Inactive(file) 7268
MemFree 291636
Wed Mar 2 06:11:55 2016
Active(file) 646904
Inactive(file) 7268
MemFree 281204
Wed Mar 2 06:11:56 2016
Active(file) 657144
Inactive(file) 7268
MemFree 270680
Wed Mar 2 06:11:57 2016
Active(file) 667392
Inactive(file) 7268
MemFree 260264
Wed Mar 2 06:11:58 2016
Active(file) 677632
Inactive(file) 7268
MemFree 249600
Wed Mar 2 06:11:59 2016
Active(file) 687872
Inactive(file) 7268
MemFree 239168
Wed Mar 2 06:12:00 2016
Active(file) 698112
Inactive(file) 7268
MemFree 228768
Wed Mar 2 06:12:01 2016
Active(file) 708352
Inactive(file) 7268
MemFree 218212
Wed Mar 2 06:12:02 2016
Active(file) 718584
Inactive(file) 7268
MemFree 207640
Wed Mar 2 06:12:03 2016
Active(file) 728840
Inactive(file) 7268
MemFree 197208
Wed Mar 2 06:12:04 2016
Active(file) 739080
Inactive(file) 7268
MemFree 186512
Wed Mar 2 06:12:05 2016
Active(file) 749320
Inactive(file) 7268
MemFree 176080
Wed Mar 2 06:12:06 2016
Active(file) 759560
Inactive(file) 7268
MemFree 165508
Wed Mar 2 06:12:07 2016
Active(file) 769808
Inactive(file) 7268
MemFree 154952
Wed Mar 2 06:12:08 2016
Active(file) 780048
Inactive(file) 7268
MemFree 144504
Wed Mar 2 06:12:10 2016
Active(file) 790300
Inactive(file) 7268
MemFree 133948
Wed Mar 2 06:12:11 2016
Active(file) 800540
Inactive(file) 7268
MemFree 123500
Wed Mar 2 06:12:12 2016
Active(file) 810780
Inactive(file) 7268
MemFree 112944
Wed Mar 2 06:12:13 2016
Active(file) 821028
Inactive(file) 7268
MemFree 102264
Wed Mar 2 06:12:14 2016
Active(file) 831268
Inactive(file) 7268
MemFree 91816
Wed Mar 2 06:12:15 2016
Active(file) 841508
Inactive(file) 7268
MemFree 81260
Wed Mar 2 06:12:16 2016
Active(file) 851748
Inactive(file) 7268
MemFree 70812
Wed Mar 2 06:12:17 2016
Active(file) 861988
Inactive(file) 7268
MemFree 60256
Wed Mar 2 06:12:18 2016
Active(file) 872236
Inactive(file) 7268
MemFree 49684
Wed Mar 2 06:12:19 2016
Active(file) 882476
Inactive(file) 7268
MemFree 39252
Wed Mar 2 06:12:20 2016
Active(file) 892716
Inactive(file) 7268
MemFree 28680
Wed Mar 2 06:12:21 2016
Active(file) 902956
Inactive(file) 7268
MemFree 18248
Wed Mar 2 06:12:22 2016
Active(file) 809036
Inactive(file) 107020
MemFree 11916
Wed Mar 2 06:12:23 2016
Active(file) 771108
Inactive(file) 148232
MemFree 9036
Wed Mar 2 06:12:24 2016
Active(file) 729564
Inactive(file) 188620
MemFree 10492
Wed Mar 2 06:12:25 2016
Active(file) 706860
Inactive(file) 212456
MemFree 9736
Wed Mar 2 06:12:26 2016
Active(file) 685596
Inactive(file) 233960
MemFree 9868
Wed Mar 2 06:12:27 2016
Active(file) 670300
Inactive(file) 250432
MemFree 8976
Wed Mar 2 06:12:28 2016
Active(file) 653200
Inactive(file) 267188
MemFree 9580
Wed Mar 2 06:12:29 2016
Active(file) 639076
Inactive(file) 281304
MemFree 9920
Wed Mar 2 06:12:30 2016
Active(file) 625416
Inactive(file) 294404
MemFree 10756
Wed Mar 2 06:12:31 2016
Active(file) 616904
Inactive(file) 304192
MemFree 9872
Wed Mar 2 06:12:32 2016
Active(file) 608672
Inactive(file) 313408
MemFree 9124
Wed Mar 2 06:12:33 2016
Active(file) 599704
Inactive(file) 322564
MemFree 9344
Wed Mar 2 06:12:34 2016
Active(file) 591000
Inactive(file) 331176
MemFree 9680
Wed Mar 2 06:12:35 2016
Active(file) 583512
Inactive(file) 338832
MemFree 9792
Wed Mar 2 06:12:36 2016
Active(file) 576248
Inactive(file) 346064
MemFree 10104
Wed Mar 2 06:12:37 2016
Active(file) 569240
Inactive(file) 352844
MemFree 10492
Wed Mar 2 06:12:38 2016
Active(file) 564560
Inactive(file) 358484
MemFree 9840
Wed Mar 2 06:12:39 2016
Active(file) 557864
Inactive(file) 364604
MemFree 10688
Wed Mar 2 06:12:40 2016
Active(file) 555524
Inactive(file) 368920
MemFree 9044
Wed Mar 2 06:12:41 2016
Active(file) 551240
Inactive(file) 373692
MemFree 8808
Wed Mar 2 06:12:43 2016
Active(file) 542976
Inactive(file) 379496
MemFree 11272
Wed Mar 2 06:12:44 2016
Active(file) 540932
Inactive(file) 383164
MemFree 10048
Wed Mar 2 06:12:45 2016
Active(file) 537024
Inactive(file) 387208
MemFree 10144
Wed Mar 2 06:12:46 2016
Active(file) 535280
Inactive(file) 390520
MemFree 8856
Wed Mar 2 06:12:47 2016
Active(file) 531516
Inactive(file) 394240
MemFree 8960
Wed Mar 2 06:12:48 2016
Active(file) 524960
Inactive(file) 398484
MemFree 11532
Wed Mar 2 06:12:49 2016
Active(file) 523316
Inactive(file) 401304
MemFree 10668
Wed Mar 2 06:12:50 2016
Active(file) 521752
Inactive(file) 404024
MemFree 9624
Wed Mar 2 06:12:51 2016
Active(file) 518004
Inactive(file) 407112
MemFree 10488
Wed Mar 2 06:12:52 2016
Active(file) 514676
Inactive(file) 409964
MemFree 11120
Wed Mar 2 06:12:53 2016
Active(file) 511444
Inactive(file) 412676
MemFree 11672
Wed Mar 2 06:12:54 2016
Active(file) 512100
Inactive(file) 414544
MemFree 9564
Wed Mar 2 06:12:55 2016
Active(file) 510424
Inactive(file) 416732
MemFree 9240
Wed Mar 2 06:12:56 2016
Active(file) 508612
Inactive(file) 418876
MemFree 9128
Wed Mar 2 06:12:57 2016
Active(file) 506692
Inactive(file) 420960
MemFree 9116
Wed Mar 2 06:12:58 2016
Active(file) 504668
Inactive(file) 422952
MemFree 9196
Wed Mar 2 06:12:59 2016
Active(file) 500872
Inactive(file) 425144
MemFree 11028
Wed Mar 2 06:13:00 2016
Active(file) 499932
Inactive(file) 426840
MemFree 10512
Wed Mar 2 06:13:01 2016
Active(file) 499008
Inactive(file) 428456
MemFree 9884
Wed Mar 2 06:13:02 2016
Active(file) 498400
Inactive(file) 430000
MemFree 8980
Wed Mar 2 06:13:03 2016
Active(file) 494780
Inactive(file) 431852
MemFree 10976
Wed Mar 2 06:13:04 2016
Active(file) 495772
Inactive(file) 433004
MemFree 8948
Wed Mar 2 06:13:05 2016
Active(file) 493212
Inactive(file) 434544
MemFree 10160
Wed Mar 2 06:13:06 2016
Active(file) 492452
Inactive(file) 435816
MemFree 9900
Wed Mar 2 06:13:07 2016
Active(file) 491728
Inactive(file) 437040
MemFree 9624
Wed Mar 2 06:13:08 2016
Active(file) 490696
Inactive(file) 438264
MemFree 9360
^C
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "At this point the systems tabilises around 490MB Active and about 430MB inactive"
At this point the systems tabilises around 490MB Active and about 430MB inactive
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "Now have a look at /proc/meminfo before and after I delete the files that we just created"
Now have a look at /proc/meminfo before and after I delete the files that we just created
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ cat /proc/meminfo
MemTotal: 1019444 kB
MemFree: 10420 kB
MemAvailable: 969860 kB
Buffers: 308 kB
Cached: 928908 kB
SwapCached: 0 kB
Active: 504448 kB
Inactive: 438452 kB
Active(anon): 13708 kB
Inactive(anon): 52 kB
Active(file): 490740 kB
Inactive(file): 438400 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 16 kB
Writeback: 0 kB
AnonPages: 13700 kB
Mapped: 4392 kB
Shmem: 60 kB
Slab: 54276 kB
SReclaimable: 44868 kB
SUnreclaim: 9408 kB
KernelStack: 1408 kB
PageTables: 2356 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 509720 kB
Committed_AS: 62876 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 2488 kB
VmallocChunk: 34359731159 kB
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 22528 kB
DirectMap2M: 1026048 kB
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ du -sh /tmp/file*
10M /tmp/file.1
10M /tmp/file.10
10M /tmp/file.100
10M /tmp/file.101
10M /tmp/file.102
10M /tmp/file.103
10M /tmp/file.104
10M /tmp/file.105
10M /tmp/file.106
10M /tmp/file.107
10M /tmp/file.108
10M /tmp/file.109
10M /tmp/file.11
10M /tmp/file.110
10M /tmp/file.111
10M /tmp/file.112
10M /tmp/file.113
10M /tmp/file.114
10M /tmp/file.115
10M /tmp/file.116
10M /tmp/file.117
10M /tmp/file.118
10M /tmp/file.119
10M /tmp/file.12
10M /tmp/file.120
10M /tmp/file.121
10M /tmp/file.122
10M /tmp/file.123
10M /tmp/file.124
10M /tmp/file.125
10M /tmp/file.126
10M /tmp/file.127
10M /tmp/file.128
10M /tmp/file.129
10M /tmp/file.13
10M /tmp/file.130
10M /tmp/file.131
10M /tmp/file.132
10M /tmp/file.133
10M /tmp/file.14
10M /tmp/file.15
10M /tmp/file.16
10M /tmp/file.17
10M /tmp/file.18
10M /tmp/file.19
10M /tmp/file.2
10M /tmp/file.20
10M /tmp/file.21
10M /tmp/file.22
10M /tmp/file.23
10M /tmp/file.24
10M /tmp/file.25
10M /tmp/file.26
10M /tmp/file.27
10M /tmp/file.28
10M /tmp/file.29
10M /tmp/file.3
10M /tmp/file.30
10M /tmp/file.31
10M /tmp/file.32
10M /tmp/file.33
10M /tmp/file.34
10M /tmp/file.35
10M /tmp/file.36
10M /tmp/file.37
10M /tmp/file.38
10M /tmp/file.39
10M /tmp/file.4
10M /tmp/file.40
10M /tmp/file.41
10M /tmp/file.42
10M /tmp/file.43
10M /tmp/file.44
10M /tmp/file.45
10M /tmp/file.46
10M /tmp/file.47
10M /tmp/file.48
10M /tmp/file.49
10M /tmp/file.5
10M /tmp/file.50
10M /tmp/file.51
10M /tmp/file.52
10M /tmp/file.53
10M /tmp/file.54
10M /tmp/file.55
10M /tmp/file.56
10M /tmp/file.57
10M /tmp/file.58
10M /tmp/file.59
10M /tmp/file.6
10M /tmp/file.60
10M /tmp/file.61
10M /tmp/file.62
10M /tmp/file.63
10M /tmp/file.64
10M /tmp/file.65
10M /tmp/file.66
10M /tmp/file.67
10M /tmp/file.68
10M /tmp/file.69
10M /tmp/file.7
10M /tmp/file.70
10M /tmp/file.71
10M /tmp/file.72
10M /tmp/file.73
10M /tmp/file.74
10M /tmp/file.75
10M /tmp/file.76
10M /tmp/file.77
10M /tmp/file.78
10M /tmp/file.79
10M /tmp/file.8
10M /tmp/file.80
10M /tmp/file.81
10M /tmp/file.82
10M /tmp/file.83
10M /tmp/file.84
10M /tmp/file.85
10M /tmp/file.86
10M /tmp/file.87
10M /tmp/file.88
10M /tmp/file.89
10M /tmp/file.9
10M /tmp/file.90
10M /tmp/file.91
10M /tmp/file.92
10M /tmp/file.93
10M /tmp/file.94
10M /tmp/file.95
10M /tmp/file.96
10M /tmp/file.97
10M /tmp/file.98
10M /tmp/file.99
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ rm /tmp/file*
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ cat /proc/meminfo
MemTotal: 1019444 kB
MemFree: 957192 kB
MemAvailable: 971072 kB
Buffers: 448 kB
Cached: 6792 kB
SwapCached: 0 kB
Active: 20508 kB
Inactive: 424 kB
Active(anon): 13708 kB
Inactive(anon): 52 kB
Active(file): 6800 kB
Inactive(file): 372 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 120 kB
Writeback: 0 kB
AnonPages: 13700 kB
Mapped: 4392 kB
Shmem: 60 kB
Slab: 29412 kB
SReclaimable: 20004 kB
SUnreclaim: 9408 kB
KernelStack: 1408 kB
PageTables: 2356 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 509720 kB
Committed_AS: 62876 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 2488 kB
VmallocChunk: 34359731159 kB
AnonHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 22528 kB
DirectMap2M: 1026048 kB
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "As you can see, the memory has freed up and the cache has disappeared"
As you can see, the memory has freed up and the cache has disappeared
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "This ladies and gentlemen has been the first installment in a series of Linux VM Subsystem experiments"
This ladies and gentlemen has been the first installment in a series of Linux VM Subsystem experiments
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "The next installment will involve the interaction of the filesystem cache and anonymous memory increases"
The next installment will involve the interaction of the filesystem cache and anonymous memory increases
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ echo "Good night, back at work in 6 hours"
Good night, back at work in 6 hours
[ec2-user@ip-172-31-37-189 linux-systems-programming]$ exit
