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Unusually high nfs_inode_cache

Mounting both /dev/sda and /dev/sda1 - how can this be?FileSize referenced in PHP Post is unusually highethernet smp_affinity vs /proc/interrupts vs /sys/class/net/ethX/devicelinux redhat 5.4 - swap while memory is still availablememory leak? RHEL 5.5. RSS show ok, almost no free memory left, swap used heavilyAnyone else experiencing high rates of Linux server crashes during a leap second day?Unusually high dentry cache usageWhere did my memory go on linux (no cache/slab/shm/ipcs)Slab usage extremely high?Where is my RAM going?

4

1

My server is experiencing a high usage of nfs_inode_cache = 11G , im trying to figure out what's consuming all this , i know already that directories with large numbers of entries and deep directory structures are searched and traversed by some java applications.

Is there any way to look into the dentry cache to see what all this memory is (what are the paths that are being cached)?

Here is my slabtop command :

   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME

8603424 8603424 100%    1.01K 2867808        3  11471232K nfs_inode_cache

3080826 3080737  99%    0.21K 171157       18    684628K dentry_cache

 24717  12515  50%    0.52K   3531        7     14124K radix_tree_node

 11365  11108  97%    0.74K   2273        5      9092K ext3_inode_cache

Here is my cache pressure :
cat /proc/sys/vm/vfs_cache_pressure
100

linux redhat memory

share|improve this question

edited Jun 17 '14 at 12:04

user1335838

asked Jun 17 '14 at 10:36

user1335838user1335838

214

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What versions of RHEL are you using? There was a known issue related to this awhile ago. access.redhat.com/solutions/481743
  
  – jeffatrackaid
  Jan 22 '15 at 19:49
  

  
  
  
  

add a comment | 

4

1

My server is experiencing a high usage of nfs_inode_cache = 11G , im trying to figure out what's consuming all this , i know already that directories with large numbers of entries and deep directory structures are searched and traversed by some java applications.

Is there any way to look into the dentry cache to see what all this memory is (what are the paths that are being cached)?

Here is my slabtop command :

   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME

8603424 8603424 100%    1.01K 2867808        3  11471232K nfs_inode_cache

3080826 3080737  99%    0.21K 171157       18    684628K dentry_cache

 24717  12515  50%    0.52K   3531        7     14124K radix_tree_node

 11365  11108  97%    0.74K   2273        5      9092K ext3_inode_cache

Here is my cache pressure :
cat /proc/sys/vm/vfs_cache_pressure
100

linux redhat memory

share|improve this question

edited Jun 17 '14 at 12:04

user1335838

asked Jun 17 '14 at 10:36

user1335838user1335838

214

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What versions of RHEL are you using? There was a known issue related to this awhile ago. access.redhat.com/solutions/481743
  
  – jeffatrackaid
  Jan 22 '15 at 19:49
  

  
  
  
  

add a comment | 

My server is experiencing a high usage of nfs_inode_cache = 11G , im trying to figure out what's consuming all this , i know already that directories with large numbers of entries and deep directory structures are searched and traversed by some java applications.

Is there any way to look into the dentry cache to see what all this memory is (what are the paths that are being cached)?

Here is my slabtop command :

   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME

8603424 8603424 100%    1.01K 2867808        3  11471232K nfs_inode_cache

3080826 3080737  99%    0.21K 171157       18    684628K dentry_cache

 24717  12515  50%    0.52K   3531        7     14124K radix_tree_node

 11365  11108  97%    0.74K   2273        5      9092K ext3_inode_cache

Here is my cache pressure :
cat /proc/sys/vm/vfs_cache_pressure
100

linux redhat memory

share|improve this question

edited Jun 17 '14 at 12:04

user1335838

asked Jun 17 '14 at 10:36

user1335838user1335838

214

   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME

8603424 8603424 100%    1.01K 2867808        3  11471232K nfs_inode_cache

3080826 3080737  99%    0.21K 171157       18    684628K dentry_cache

 24717  12515  50%    0.52K   3531        7     14124K radix_tree_node

 11365  11108  97%    0.74K   2273        5      9092K ext3_inode_cache

share|improve this question

edited Jun 17 '14 at 12:04

user1335838

asked Jun 17 '14 at 10:36

user1335838user1335838

214

share|improve this question

edited Jun 17 '14 at 12:04

user1335838

asked Jun 17 '14 at 10:36

user1335838user1335838

214

asked Jun 17 '14 at 10:36

user1335838user1335838

214

asked Jun 17 '14 at 10:36

user1335838user1335838

214

1 Answer
1

active

oldest

votes

1

Are you experiencing any issue? What does your RAM usage looks like? (ex. free -m)

It's perfectly normal for Linux to use whatever's RAM available for caching - some of it will show through slabtop (dentries, inodes, etc.) and the rest through free -m' cached memory (pagecache/swapcache).

/proc/sys/vm/vfs_cache_pressure controls the proportions by which the kernel will free them. 100 is the default "fair" setting. Reducing this value favors pruning pagecache (i.e. file contents) while increasing it favors pruning filesystem metadata (inodes, etc...). In any case, cache pruning will happen only under memory presure; if you have plenty of unused memory the kernel will keep it used for caching.

Probably a much more important setting is vm.swappiness - this one controls the kernel's behavior to swap out memory vs. reclaim cache memory. The default value is good in most cases, but if you see processes hung/swapped out during periods of intensive IO with way more cached ram than you need then you most likely want to reduce this one. Additionally, if you have huge amount of memory and a fairly old kernel you may need to adjust one of these parameters as well (either the *bytes or *ratio, not both!):

• dirty_background_bytes


• dirty_background_ratio


• dirty_bytes


• dirty_ratio

All these settings are fully documented here: https://www.kernel.org/doc/Documentation/sysctl/vm.txt

However if you're not experiencing any issue, hung processes, excessive swapping out, etc. then I suggest not changing the defaults.

share|improve this answer

edited 1 min ago

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114

add a comment | 

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1

Are you experiencing any issue? What does your RAM usage looks like? (ex. free -m)

It's perfectly normal for Linux to use whatever's RAM available for caching - some of it will show through slabtop (dentries, inodes, etc.) and the rest through free -m' cached memory (pagecache/swapcache).

/proc/sys/vm/vfs_cache_pressure controls the proportions by which the kernel will free them. 100 is the default "fair" setting. Reducing this value favors pruning pagecache (i.e. file contents) while increasing it favors pruning filesystem metadata (inodes, etc...). In any case, cache pruning will happen only under memory presure; if you have plenty of unused memory the kernel will keep it used for caching.

Probably a much more important setting is vm.swappiness - this one controls the kernel's behavior to swap out memory vs. reclaim cache memory. The default value is good in most cases, but if you see processes hung/swapped out during periods of intensive IO with way more cached ram than you need then you most likely want to reduce this one. Additionally, if you have huge amount of memory and a fairly old kernel you may need to adjust one of these parameters as well (either the *bytes or *ratio, not both!):

• dirty_background_bytes


• dirty_background_ratio


• dirty_bytes


• dirty_ratio

All these settings are fully documented here: https://www.kernel.org/doc/Documentation/sysctl/vm.txt

However if you're not experiencing any issue, hung processes, excessive swapping out, etc. then I suggest not changing the defaults.

share|improve this answer

edited 1 min ago

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114

add a comment | 

1

Are you experiencing any issue? What does your RAM usage looks like? (ex. free -m)

It's perfectly normal for Linux to use whatever's RAM available for caching - some of it will show through slabtop (dentries, inodes, etc.) and the rest through free -m' cached memory (pagecache/swapcache).

/proc/sys/vm/vfs_cache_pressure controls the proportions by which the kernel will free them. 100 is the default "fair" setting. Reducing this value favors pruning pagecache (i.e. file contents) while increasing it favors pruning filesystem metadata (inodes, etc...). In any case, cache pruning will happen only under memory presure; if you have plenty of unused memory the kernel will keep it used for caching.

Probably a much more important setting is vm.swappiness - this one controls the kernel's behavior to swap out memory vs. reclaim cache memory. The default value is good in most cases, but if you see processes hung/swapped out during periods of intensive IO with way more cached ram than you need then you most likely want to reduce this one. Additionally, if you have huge amount of memory and a fairly old kernel you may need to adjust one of these parameters as well (either the *bytes or *ratio, not both!):

• dirty_background_bytes


• dirty_background_ratio


• dirty_bytes


• dirty_ratio

All these settings are fully documented here: https://www.kernel.org/doc/Documentation/sysctl/vm.txt

However if you're not experiencing any issue, hung processes, excessive swapping out, etc. then I suggest not changing the defaults.

share|improve this answer

edited 1 min ago

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114

add a comment | 

Are you experiencing any issue? What does your RAM usage looks like? (ex. free -m)

It's perfectly normal for Linux to use whatever's RAM available for caching - some of it will show through slabtop (dentries, inodes, etc.) and the rest through free -m' cached memory (pagecache/swapcache).

/proc/sys/vm/vfs_cache_pressure controls the proportions by which the kernel will free them. 100 is the default "fair" setting. Reducing this value favors pruning pagecache (i.e. file contents) while increasing it favors pruning filesystem metadata (inodes, etc...). In any case, cache pruning will happen only under memory presure; if you have plenty of unused memory the kernel will keep it used for caching.

Probably a much more important setting is vm.swappiness - this one controls the kernel's behavior to swap out memory vs. reclaim cache memory. The default value is good in most cases, but if you see processes hung/swapped out during periods of intensive IO with way more cached ram than you need then you most likely want to reduce this one. Additionally, if you have huge amount of memory and a fairly old kernel you may need to adjust one of these parameters as well (either the *bytes or *ratio, not both!):

• dirty_background_bytes


• dirty_background_ratio


• dirty_bytes


• dirty_ratio

All these settings are fully documented here: https://www.kernel.org/doc/Documentation/sysctl/vm.txt

However if you're not experiencing any issue, hung processes, excessive swapping out, etc. then I suggest not changing the defaults.

share|improve this answer

edited 1 min ago

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114

share|improve this answer

edited 1 min ago

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114

answered May 13 '15 at 5:10

Thomas Guyot-SionnestThomas Guyot-Sionnest

31114