After increasing chunksize in an LVM cache, files are no longer promoted to the cache
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After running into issues with running out of kernel memory, I increased the chunksize of my lvmcache from the default (which I believe was 64k) to a much higher 8M.
After this change, blocks do not seem to be promoted to the cache, despite constant use with both reads and writes. The meta cache is being used however (at a roughly similar rate to before the chunksize change).
The cache was created in writeback mode.
media-media: 0 46883430400 cache 8 277/2621440 16384 0/56320 0 2903157 0 1259187 0 0 0 1 writeback 2 migration_threshold 2048 smq 0 rw -
Is there a way to investigate why blocks are not being promoted? I understand this large chunk size will likely be a lot less efficient in the general case, but surely some blocks should be promoted?
linux lvm cache device-mapper
asked Aug 5 '17 at 14:40
ss23
217
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up vote
1
down vote
favorite
After running into issues with running out of kernel memory, I increased the chunksize of my lvmcache from the default (which I believe was 64k) to a much higher 8M.
After this change, blocks do not seem to be promoted to the cache, despite constant use with both reads and writes. The meta cache is being used however (at a roughly similar rate to before the chunksize change).
The cache was created in writeback mode.
media-media: 0 46883430400 cache 8 277/2621440 16384 0/56320 0 2903157 0 1259187 0 0 0 1 writeback 2 migration_threshold 2048 smq 0 rw -
Is there a way to investigate why blocks are not being promoted? I understand this large chunk size will likely be a lot less efficient in the general case, but surely some blocks should be promoted?
linux lvm cache device-mapper
asked Aug 5 '17 at 14:40
ss23
217
add a comment |
up vote
1
down vote
favorite
up vote
1
down vote
favorite
After running into issues with running out of kernel memory, I increased the chunksize of my lvmcache from the default (which I believe was 64k) to a much higher 8M.
After this change, blocks do not seem to be promoted to the cache, despite constant use with both reads and writes. The meta cache is being used however (at a roughly similar rate to before the chunksize change).
The cache was created in writeback mode.
media-media: 0 46883430400 cache 8 277/2621440 16384 0/56320 0 2903157 0 1259187 0 0 0 1 writeback 2 migration_threshold 2048 smq 0 rw -
Is there a way to investigate why blocks are not being promoted? I understand this large chunk size will likely be a lot less efficient in the general case, but surely some blocks should be promoted?
linux lvm cache device-mapper
asked Aug 5 '17 at 14:40
ss23
217
After running into issues with running out of kernel memory, I increased the chunksize of my lvmcache from the default (which I believe was 64k) to a much higher 8M.
After this change, blocks do not seem to be promoted to the cache, despite constant use with both reads and writes. The meta cache is being used however (at a roughly similar rate to before the chunksize change).
The cache was created in writeback mode.
media-media: 0 46883430400 cache 8 277/2621440 16384 0/56320 0 2903157 0 1259187 0 0 0 1 writeback 2 migration_threshold 2048 smq 0 rw -
Is there a way to investigate why blocks are not being promoted? I understand this large chunk size will likely be a lot less efficient in the general case, but surely some blocks should be promoted?
linux lvm cache device-mapper
linux lvm cache device-mapper
asked Aug 5 '17 at 14:40
ss23
217
asked Aug 5 '17 at 14:40
ss23
217
asked Aug 5 '17 at 14:40
ss23
217
asked Aug 5 '17 at 14:40
ss23
217
asked Aug 5 '17 at 14:40
ss23
217
217
add a comment |
add a comment |
1 Answer
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0
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Sorry for digging graves, but I happens to find a similar problem.
It seems the LVM cache has problem with cache chunk size larger than 1M.
(https://marc.info/?l=linux-lvm&m=152948734523317&w=2)
In my case the chunk size is 1.06M, which was determined by the lvcreate command automatically.
The cache was created in writethrough mode. Then I changed it to writeback, the block promotes; but when I try to flush the cache, the dirty blocks cannot be written to the disk.
I have to destroy the whole LV, since the cache cannot be split safely. Recreate the cachepool with --chunksize=512k and the cache flushing works.
Are you still using LVM cache? What's your current cache chunk size?
answered Nov 29 at 19:40
Mike Chen
11
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Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
Sorry for digging graves, but I happens to find a similar problem.
It seems the LVM cache has problem with cache chunk size larger than 1M.
(https://marc.info/?l=linux-lvm&m=152948734523317&w=2)
In my case the chunk size is 1.06M, which was determined by the lvcreate command automatically.
The cache was created in writethrough mode. Then I changed it to writeback, the block promotes; but when I try to flush the cache, the dirty blocks cannot be written to the disk.
I have to destroy the whole LV, since the cache cannot be split safely. Recreate the cachepool with --chunksize=512k and the cache flushing works.
Are you still using LVM cache? What's your current cache chunk size?
answered Nov 29 at 19:40
Mike Chen
11
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
add a comment |
up vote
0
down vote
Sorry for digging graves, but I happens to find a similar problem.
It seems the LVM cache has problem with cache chunk size larger than 1M.
(https://marc.info/?l=linux-lvm&m=152948734523317&w=2)
In my case the chunk size is 1.06M, which was determined by the lvcreate command automatically.
The cache was created in writethrough mode. Then I changed it to writeback, the block promotes; but when I try to flush the cache, the dirty blocks cannot be written to the disk.
I have to destroy the whole LV, since the cache cannot be split safely. Recreate the cachepool with --chunksize=512k and the cache flushing works.
Are you still using LVM cache? What's your current cache chunk size?
answered Nov 29 at 19:40
Mike Chen
11
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
add a comment |
up vote
0
down vote
up vote
0
down vote
Sorry for digging graves, but I happens to find a similar problem.
It seems the LVM cache has problem with cache chunk size larger than 1M.
(https://marc.info/?l=linux-lvm&m=152948734523317&w=2)
In my case the chunk size is 1.06M, which was determined by the lvcreate command automatically.
The cache was created in writethrough mode. Then I changed it to writeback, the block promotes; but when I try to flush the cache, the dirty blocks cannot be written to the disk.
I have to destroy the whole LV, since the cache cannot be split safely. Recreate the cachepool with --chunksize=512k and the cache flushing works.
Are you still using LVM cache? What's your current cache chunk size?
answered Nov 29 at 19:40
Mike Chen
11
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Sorry for digging graves, but I happens to find a similar problem.
It seems the LVM cache has problem with cache chunk size larger than 1M.
(https://marc.info/?l=linux-lvm&m=152948734523317&w=2)
In my case the chunk size is 1.06M, which was determined by the lvcreate command automatically.
The cache was created in writethrough mode. Then I changed it to writeback, the block promotes; but when I try to flush the cache, the dirty blocks cannot be written to the disk.
I have to destroy the whole LV, since the cache cannot be split safely. Recreate the cachepool with --chunksize=512k and the cache flushing works.
Are you still using LVM cache? What's your current cache chunk size?
answered Nov 29 at 19:40
Mike Chen
11
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited Nov 29 at 21:20
answered Nov 29 at 19:40
Mike Chen
11
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered Nov 29 at 19:40
Mike Chen
11
answered Nov 29 at 19:40
Mike Chen
11
11
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Mike Chen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
add a comment |
I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
I never found a solution so have migrated away from lvm based caching. Tweaking my chunk size manually got it caching again, but it was a bit of a black-box, so not something I wanted to continue using.
– ss23
2 days ago
add a comment |
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