Add post: linux:using zram

2 files changed, 96 insertions, 1 deletions

diff --git a/posts/index.adoc b/posts/index.adoc
index 47d6fc0..601a259 100644
--- a/posts/index.adoc
+++ b/posts/index.adoc
@@ -7,6 +7,7 @@ Home
 [role="index"]
 New Posts
 ---------
+* link:?p=linux:using-zram[Linux:Using ZRam]
 * link:?p=Circumventing_MacOS_FileVault_Autologin_Restrictions[Circumventing MacOS FileVault Autologin Restrictions]
 * link:?p=bash:handy_bashrc_bits[Bash:Handy Bashrc Bits]
 * link:?p=librem5-cant-update-404-not-found[Librem 5:Can't Update - 404 Not found]
@@ -19,7 +20,6 @@ New Posts
 * link:?p=how_to_uninterest_me_in_your_job_opening[How to Uninterest Me in Your Job Opening]
 * link:?p=why-linux-is-hard[Why Linux is Hard]
 * link:?p=checking-dnsbl-lists[Checking DNSBL Lists]
-* link:?p=linux:non-root-suspend[Linux:Non-root Suspend]
 
 [role="index"]
 Purism Librem 5
@@ -32,6 +32,7 @@ Purism Librem 5
 [role="index"]
 Linux
 -----
+* link:?p=linux:using-zram[Linux:Using ZRam]
 * link:?p=why-linux-is-hard[Why Linux is Hard]
 * link:?p=linux:manual_restart_with_sysrq-trigger[Linux:Manual Restart with sysrq-trigger]
 * link:?p=crux_linux:faster_builds[Crux Linux:Faster Builds]
diff --git a/posts/linux:using-zram.rst b/posts/linux:using-zram.rst
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+Linux:Using ZRam
+=================
+
+I recently discovered zram in Linux, and it felt like a mystical, futuristic
+experience. Upon discovering it and learning how to use it, I immediately went
+looking for uses.
+
+
+What is Zram?
+-------------
+
+`Zram <https://www.kernel.org/doc/html/latest/admin-guide/blockdev/zram.html>`_
+is a feature of the Linux kernel (``modprobe zram``) that allows the user to
+create "compressed RAM-based block devices".
+
+If that doesn't make much sense, it is very similar to RAM drives, but
+compressed. I learned about using RAM drives a few years ago (``mount -t tmpfs
+...``) and have been using them for all kinds of things on my systems to reduce
+IO load on my storage, while maximizing performance. With RAM drives you
+section off a portion of your RAM to use as "storage" [with a read/write speed
+of ~6 GB/s]. ZRam is very similar, except that it compresses inline, making
+even more "storage" available at the cost of less RAM, but slightly higher CPU.
+
+
+How can we use zram?
+--------------------
+
+A package compiling layer (like /var/pkgmk)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously, I did this (in fstab, but here's the command)
+
+.. code-block:: sh
+
+   mount -t tmpfs -o size=10G none /var/pkgmk
+
+That creates a 10 GB RAM device, mounted at ``/var/pkgmk``, where I compile
+packages from source on my system (any Crux users out there?).
+
+NOW however, I do this:
+
+.. code-block:: sh
+
+   dev=$(zramctl -f)  # Find the first available zram device
+   zramctl "${dev}" -s 16384 -t $(( $(nproc) / 2 ))
+   mkfs.ext4 "${dev}"
+   mount "${dev}" /var/pkgmk
+
+It's a bit more complicated to get set up (I have the above in a script), but
+the end result is a 16 GB RAM drive, which takes significantly less ram, using
+up to half of my CPU's cores to compress. I tend to see about 70% compression
+when compiling source code, so while the drive allows for 16 GB of capacity
+(the full amount in my laptop in fact), at its maximum it only takes about 5
+GB; usually much less.
+
+
+zswap (swapon... swapoff... swapon... swapoff)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+I haven't used swap on my system in a long time. With computers coming with
+more and more RAM, I haven't needed it in a long time. However, I recently ran
+into some compiling tasks that, combined with my ram drive for storing
+compiling source code, consumes more RAM than my laptop has.
+
+Enter ``zswap``
+
+Zswap is basically the same thing as a zram block device, except instead of
+being formatted with a real filesystem, it is formatted for swap usage. To set
+one of these up, I do this (again, this is distilled from the script I wrote):
+
+.. code-block:: sh
+
+   dev=$(zramctl -f)  # Find the first available zram device
+   zramctl "${dev}" -s 10240 -t $(( $(nproc) / 2 ))
+   mkswap "${dev}"
+   swapon "${dev}"
+
+That will create a new zram block device that is 10 GB in size, using up to
+half of my CPU's cores for compression. This zram device is then formatted for
+swap usage (``mkswap``), and enabled (``swapon``).
+
+
+
+Conclusion
+----------
+
+These commands obviously need to be put into a nice shell script for easy setup
+and teardown. I have my in an init script, supporting ``start``, ``stop``, and
+``status`` commands to make things less cumbersome. You can see the full init
+script I wrote for zswap setup over `here
+<https://oper.io/src/nullspoon/zram-swap.git/>`_.
+
+Do you have any other ideas for how to use zram? If so, feel free to email me
+any ideas you might come up with. I'd love to hear them!