> Enable ESwap before zram is enabled. If ESwap is not used, you can enable zram alone. If a device does not have the storage device for swap-out or have the corresponding storage partition created, you can enable zram to reclaim memory using **zswapd**.
### Enabling ESwap
1. Enable related configuration items and dependencies.
To enable ESwap, you must enable the corresponding configuration items and dependencies during kernel compilation. The configuration items related to ESwap are as follows:
CONFIG_HYPERHOLD_MEMCG=y // Enable Memcg management in Hyperhold
CONFIG_ZRAM_GROUP=y // Enable Manage Zram objs with mem_cgroup
CONFIG_ZRAM_GROUP_DEBUG=y // Enable Manage Zram objs with mem_cgroup Debug
CONFIG_ZLIST_DEBUG=y // Enable Debug info for zram group list
CONFIG_ZRAM_GROUP_WRITEBACK=y // Enable write back grouped zram objs to Hyperhold driver
```
Enable the following dependencies:
```
CONFIG_MEMCG=y
CONFIG_SWAP=y
CONFIG_ZSMALLOC=y
CONFIG_ZRAM=y
CONFIG_MEMCG=y // Enable memory controller
CONFIG_SWAP=y // Enable paging of anonymous memory (swap)
CONFIG_ZSMALLOC=y // Enable memory allocator for compressed pages
CONFIG_ZRAM=y // Enable compressed RAM block device support
```
2. Create an ESwap device.
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@@ -56,11 +59,11 @@ Enhanced Swap (ESwap) allows a custom partition to serve as a swap partition and
By default, ESwap encrypts the data swapped out. If the ESwap device created in step 2 supports inline encryption, you can disable the ESwap software encryption function.
```Bash
// Check whether hardware-based encryption is supported and enabled. If yes, disable software encryption. Otherwise, do not perform this operation.
// Check whether hardware-based encryption is supported and enabled. If yes, disable software encryption. Otherwise, do not disable software encryption.
> For security purposes, all swapped content must be encrypted. If the ESwap device created does not support inline encryption or the inline encryption macro is not enabled during compilation, ESwap cannot be enabled after software encryption is disabled.
4. Enable ESwap.
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...
@@ -72,9 +75,6 @@ Enhanced Swap (ESwap) allows a custom partition to serve as a swap partition and
> Enable ESwap before zram is enabled. If ESwap is not used, you can enable zram only. If a device does not have the storage device for swap-out or have the corresponding storage partition created, you can enable zram to reclaim memory using **zswapd**.
### Enabling zram
1. Initialize zram.
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...
@@ -88,7 +88,7 @@ Enhanced Swap (ESwap) allows a custom partition to serve as a swap partition and
> The difference of the two commands is as follows:
>
> - **disable**: If there is no data in the ESwap partition, disable ESwap. Otherwise, changes ESwap to **readonly** mode.
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@@ -132,42 +132,46 @@ Enhanced Swap (ESwap) allows a custom partition to serve as a swap partition and
## ESwap APIs
ESwap provides APIs to control swap-in and swap-out policies and record the current status. These APIs are located in the directory to which memcg is mounted, for example, `/dev/memcg/`.
ESwap provides APIs to control swap-in and swap-out policies and record the current status. These APIs are located in the directory to which memcg is mounted, for example, **/dev/memcg/**.
| Category| API| Description|
| -------- | -------- | -------- |
| Control| [avail_buffers](#avail_buffers) | Sets the buffer range.|
> Only **avail_buffers** proactively wakes up zswapd because the buffer waterline is adjusted. Other control APIs do not proactively wake up zswapd, but their configuration takes effect only after zswapd is woken up.
The APIs are described as follows:
### avail_buffers
The **avail_buffers** API sets the buffer range [min_avail_buffers, high_avail_buffers]. When the current buffer is less than the value of **min_avail_buffers**, zswapd will be woken up to reclaim anonymous pages. The expected amount of memory to reclaim is the difference between the value of **high_avail_buffers** and the current system buffer value. In fact, less memory is reclaimed due to reasons such as reclamation failure.
The parameters include the following:
-**avail_buffers** indicates the expected buffer value.
-**avail_buffers** indicates the expected buffer value.
-**free_swap_threshold** indicates the threshold of the free capacity of the swap partition. After zswapd is woken up to reclaim memory, press events, such as medium press and critical press, will be recorded based on the current system status and the settings of these two parameters.
You can proactively adjust the values to trigger zswapd reclamation.
Example:
You can proactively adjust the values to trigger zswapd reclamation.
@@ -207,17 +215,21 @@ The values are all integers.
### zram_wm_ratio
The **zram_wm_ratio** API sets the zram swap-out waterline. When the size of the compressed anonymous page in the zram partition is greater than the total size of zram multiplied by **zram_wm_ratio**, the page is swapped out to the ESwap partition. The swap is performed after zswapd is woken up by the buffer waterline. The system defaults the value **0** as **37**. You can change the value as required.
Example:
**zram_wm_ratio** sets the zram swap-out waterline. When the size of the compressed anonymous page in the zram partition is greater than the total size of zram multiplied by **zram_wm_ratio**, the page is swapped out to the ESwap partition. The swap is performed after zswapd is woken up by the buffer waterline. The system defaults the value **0** as **37**.
You can change the value as required.
**Example**:
`echo 30 > /dev/memcg/memory.zram_wm_ratio`
Default value:
**Default value**:
```
zram_wm_ratio: 0
zram_wm_ratio: 0
```
Limit:
**Limit**:
0<=zram_wm_ratio<=100
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@@ -225,7 +237,7 @@ The value is an integer.
### zswapd_pressure_show
The **zswapd_pressure_show** API records the zswapd status. **buffer_size** indicates the current buffer size of the system, and **recent_refault** indicates the number of refaults occurred.
**zswapd_pressure_show** records the zswapd status. **buffer_size** indicates the current buffer size of the system, and **recent_refault** indicates the number of refaults occurred.
### stat
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@@ -235,12 +247,12 @@ In addition to **memcg.stat**, the **stat** API is added with **Anon**, **File**
### zswapd_vmstat_show
The **zswapd_vmstat_show** API records events occurred during the zswapd running.
**zswapd_vmstat_show** records events occurred during the zswapd running.
## Triggering zswapd
You can check the current buffer value by running `cat /dev/memcg/memory.zswapd_pressure_show`. For example, if the current buffer value is 1200, you can adjust the buffer range to wake up zswapd.
You can run **cat /dev/memcg/memory.zswapd_pressure_show** to check the current buffer value. For example, if the current buffer value is 1200, you can adjust the buffer range to a value greater than 1200 to wake up zswapd.
