[dm-devel] mirror target memory consumption

[Eli Malul]

Could someone please help out with this? This memory consumption is
preventing me from working with the device mapper...

 

I created a mapped device with a table consisting 10, 20 and 30 mirror
targets to examine the memory consumption.

You can see that the memory consumption is very high (in terms of mega).

 

I also verified that CONFIG_BLK_DEV_INTEGRITY is disabled.

 

Do you have any idea why does a mirror target consumes so much memory?

 

For 10 mirror targets the memory consumption is ~7M:

==========================================

[root at vpc09 ~]# free -m

total      used       free     shared   buffers cached

Mem:                                    7837      566          7271    0
105        372

-/+ buffers/cache:                           88           7749

Swap:                                    0              0              0

[root at vpc09 ~]# dmsetup create mirror_dev /tmp/mirror_core_sync_10.txt

[root at vpc09 ~]# free -m

total       used      free     shared    buffers  cached

Mem:                                    7837       573         7264    0
105        372

-/+ buffers/cache:                           95           7742

Swap:                                    0              0              0

 

For 20 mirror targets the memory consumption is ~12M:

===========================================

[root at vpc09 ~]# dmsetup remove mirror_dev

[root at vpc09 ~]# free -m

total      used       free     shared   buffers cached

Mem:                                    7837      566          7271    0
105        372

-/+ buffers/cache:                           89           7749

Swap:                                    0              0              0

 

[root at vpc09 ~]# dmsetup create mirror_dev /tmp/mirror_core_sync_20.txt

[root at vpc09 ~]# free -m

total      used       free     shared   buffers cached

Mem:                                    7837      580          7257    0
106        372

-/+ buffers/cache:                           101         7736

Swap:                                    0              0              0

 

For 30 mirror targets the memory consumption is ~19M:

===========================================

[root at vpc09 ~]# dmsetup remove mirror_dev

[root at vpc09 ~]# free -m

total      used       free     shared   buffers cached

Mem:                                    7837      568          7269    0
106        372

-/+ buffers/cache:                           89           7748

Swap:                                    0              0              0

 

[root at vpc09 ~]# dmsetup create mirror_dev /tmp/mirror_core_sync_30.txt

[root at vpc09 ~]# free -m

total      used       free     shared   buffers cached

Mem:                                    7837      587          7250    0
106        372

-/+ buffers/cache:                           108         7729

Swap:                                    0              0              0

 

This is how the mapped file table looks like (you get the picture for
the other 20 and 30 target files):

========================================================================
====

[root at vpc09 ~]# cat /tmp/mirror_core_sync_10.txt

0 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

8 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

16 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

24 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

32 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

40 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

48 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

56 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

64 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

72 8 mirror core 2 8 sync 2 /dev/loop0 0 /dev/loop1 0

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