Questions tagged [zswap]
8 questions
27
votes
2 answers
Get current zswap memory usage and statistics
The zswap documentation says:
Zswap seeks to be simple in its policies. Sysfs attributes allow for one user
controlled policy:
* max_pool_percent - The maximum percentage of memory that the compressed
pool can occupy.
This specifies the…
Tom Hale
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8
votes
1 answer
Prevent zram LRU inversion with zswap and max_pool_percent = 100
The major disadvantage of using zram is LRU inversion:
older pages get into the higher-priority zram and quickly fill it, while newer pages are swapped in and out of the slower [...] swap
The zswap documentation says that zswap does not suffer…
Tom Hale
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5
votes
1 answer
Compress swap pages written to disk
This answer says that zswap decompresses pages before writing them to non-RAM swap.
Is there any way to compress the pages written to disk, ideally with lz4?
I hope to:
Reduce SSD write wear
Reduce swap disk allocation
Speed up swap IO (hopefully…
Tom Hale
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1
vote
2 answers
Effect of enabling zswap on zram without any disk swap
I have set up a system that has 4 GB RAM with 1.5 GiB of zram. It also has zswap enabled. I don't have any swap partition on the secondary storage.
As I have noticed, the performance is good on my systems.
Is the zswap being used on zram? Can using…
15 Volts
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1
vote
1 answer
Which process (kernel thread) is doing the actual compression for zswap?
I can imagine actually two locations:
In the kernel space belonging to the process whose ram is being swapped in/out
From [kswapd0]
However, digging into the kswapd source (mm/vmscan.c, init/main.c), I could find: kswapd is single-threaded, and is…
peterh
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0
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0 answers
Recommended kernel parameters for zswap
There are a lot of proposals for this in the zram context, but not for zswap. What would be acceptable kernel parameters?
vm.swappiness=100 (or even higher?)
vm.vfs_cache_pressure=500 (really?)
vm.oom_kill_allocating_task=1
vm.page-cluster = 0 …
mav
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0
votes
1 answer
CentOS 7 can Zswap be used? How to monitor Zswap? Is this a good idea?
Does CentOS 7 support Zswap? If so, how do I enable it and how to test to see if its working? Is this a good idea for a CentOS server?
Enable attempt:
chmod 777 /sys/module/zswap/parameters/enabled;echo 1 > /sys/module/zswap/parameters/enabled;…
Jeff Luyet
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0
votes
1 answer
When is zswap used?
I would like to reduce the wear of my SSD.
I'm trying to understand the mechanics of zswap:
Is zswap only used after the uncompresed swap is full?
If no, what is the allocation policy?
Tom Hale
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