{"id":47110,"date":"2024-08-26T16:18:48","date_gmt":"2024-08-26T16:18:48","guid":{"rendered":"https:\/\/ubuntuhandbook.org\/?p=47110"},"modified":"2024-09-06T08:17:01","modified_gmt":"2024-09-06T08:17:01","slug":"enable-zswap-ubuntu","status":"publish","type":"post","link":"https:\/\/ubuntuhandbook.org\/index.php\/2024\/08\/enable-zswap-ubuntu\/","title":{"rendered":"How to Enable Zswap for Ubuntu 24.04 PC with Limited RAM"},"content":{"rendered":"

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This tutorial shows how to enable zswap kernel module to increase usable RAM in your Ubuntu computer or laptop.<\/p>\n

As you know, Ubuntu Linux usually includes a swap space (either disk partition or swap file) on the disk. It can be used for hibernation, and as extended memory space. When the system needs more memory resources and the RAM is going full, then the inactive pages in memory are moved to the swap space.<\/p>\n

Swap space can be helpful for computers with limited RAM. But, it’s slow! Too much swap in use will slow down the overall system performance.<\/p>\n

As workarounds, Linux includes 2 kernel modules: zram<\/b> and zswap<\/b>. Instead of moving inactive pages from memory to disk (swap space), they do similar things by compressing the data into dynamically allocated RAM space.<\/p>\n

As the data is compressed, it takes less physical memory space which makes your RAM even more usable. While, keeping the system running smoothly because reading from compressed data in RAM is usually faster than reading from swap on disk.<\/p>\n

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zram and zswap<\/h3>\n

zram<\/b> creates a block device in RAM, that acts as swap space (or a general-purpose RAM disk). When system needs to swap out inactive pages, zram compress them into the block device. No swap on disk is required.<\/p>\n

zswap<\/b> is a lightweight compressed RAM cache for swap pages. It attempts to compress the pages, that are needed to swap out, and store them into a memory pool in RAM. Poorly compressible data is directly written to disk (swap space). And, when the memory pool is full or the RAM is exhausted, the least recently used page is decompressed and written to disk (swap). A swap space on disk is required!<\/p>\n

Both zram and zswap do NOT use any RAM initially. They dynamically grow or shrink RAM usage as required. The difference is that zram works as swap space with higher priority, so hibernation won’t work normally. While zswap needs a swap space on disk to work along with.<\/p>\n

Use zram or zswap is a good choice for computer with small amount of RAM, or for large apps\/games that need more memory than physical RAM capacity.<\/b><\/p>\n

However, if you have a plenty of RAM that rarely uses swap space, or you’re CPU-bound (bottlenecked by the CPU), then you may stay away from them, because they consume more CPU for compressing\/decompressing.<\/b><\/p>\n

Option 1: Enable Zswap in Run-time<\/h3>\n

If you need swap for hibernation feature, then zswap<\/a> is the better choice. All current Ubuntu releases have the kernel module loaded by default, all you need to do is just enable the function and do few parameter changes.<\/p>\n

1.<\/b> First, press Ctrl+Alt+T<\/code> on keyboard to open up a terminal window. Then, run command to check current zswap module parameters:<\/p>\n

systool -v -m zswap<\/pre>\n
Run sudo apt install sysfsutils<\/code> if command not found.<\/i> In the terminal output, it should print that “enabled = “N”” meaning the feature is not enabled.<\/p>\n
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All the module parameters can be modified by the config files under \/sys\/module\/zswap\/parameters\/<\/code> directory. They include:<\/p>\n