krcu cmap relocated to medium

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+# krcu-cmap
+
+- source: [linuxyz/krcu-cmap](https://github.com/seantywork/linuxyz/tree/main/krcu-cmap)
+- date: 2509-24
+
+# 01
+
+```shell
+# a regular old concurrent map...
+concurrent_map
+|     bucket_count
+|     bucket_0-------
+|     |     spin_lock      
+|     |     node_0----node_1----node_n
+|     bucket_1-------
+|     |     spin_lock
+|     |     node_0----node_1----node_n
+|     bucket_2-------
+|     |     spin_lock
+|     |     node_0----node_1----node_n
+|     bucket_n-------
+|     |     spin_lock
+|     |     node_0----node_1----node_n
+|     ----------------
+|     |
+---------------
+```
+# 02
+
+```c
+struct node {
+    int key;
+    int value;
+       struct list_head _node; 
+       struct rcu_head _rcu; // <----- hello!
+};
+```
+
+# 03
+
+```shell
+
+|---(r)eader thread------------|---(w)riter thread-----------|
+|    wait for cmap to be ready |                             |
+|                              |   create cmap               |
+|                              |   update cmap (fill up)     |
+|                              |   ready!                    |
+|                              |                             |
+|    read values from cmap     |   update cmap               |
+|    (interval 100ms)          |   (interval 1000ms)         |
+|    continue                  |   continue                  |
+|    continue                  |   continue                  |
+|    continue                  |   continue                  |
+|    continue                  |   delete all nodes          |
+|    continue...               |   exit                      |
+|    untile there is no value  |                             |
+|    (sum == 0)                |                             |
+|    exit                      |                             |
+--------------------------------------------------------------
+```
+
+# 04
+
+```shell
+$ make
+```
+ # 05
+
+```shell
+
+$ sudo dmesg -wH
+```
+
+# 06
+
+```shell
+$ sudo insmod rcucmap.ko
+```
+
+```shell
+# `dmesg -wH` output
+[Sep24 09:06] r: init
+[  +0.000007] r: wait...
+[  +0.000087] w: init
+[  +0.000038] w: updating cmap
+[  +0.000003] w: update cmap: 0
+[  +0.000001] w: update cmap: 5
+[  +0.000001] w: update cmap: 2
+[  +0.000001] w: update cmap: 9
+[  +0.000001] w: update cmap: 5
+[  +0.000001] w: update cmap: 2
+[  +0.000000] w: update cmap: 8
+[  +0.000001] w: update cmap: 3
+[  +0.000001] w: update cmap: 1
+[  +0.000000] w: update cmap: 7
+[  +0.000001] w: ready
+[  +0.103514] r: run
+[  +0.000017] r: continue: sum: 45
+[  +0.100011] r: continue: sum: 45
+[  +0.100018] r: continue: sum: 45
+[  +0.100057] r: continue: sum: 45
+[  +0.100018] r: continue: sum: 45
+[  +0.100015] r: continue: sum: 45
+[  +0.100015] r: continue: sum: 45
+[  +0.100016] r: continue: sum: 45
+[  +0.100020] r: continue: sum: 45
+[  +0.100021] r: continue: sum: 45
+[  +0.100025] r: continue: sum: 45
+[  +0.100070] r: continue: sum: 45
+[  +0.100025] r: continue: sum: 45
+[  +0.100032] r: continue: sum: 45
+[  +0.100033] r: continue: sum: 45
+[  +0.100060] r: continue: sum: 45
+[  +0.100054] r: continue: sum: 45
+[  +0.100030] r: continue: sum: 45
+[  +0.100021] r: continue: sum: 45
+[  +0.100018] r: continue: sum: 90
+[  +0.100021] r: continue: sum: 90
+[  +0.100018] r: continue: sum: 90
+[  +0.100021] r: continue: sum: 90
+[  +0.100019] r: continue: sum: 90
+[  +0.100017] r: continue: sum: 90
+[  +0.100016] r: continue: sum: 90
+[  +0.100025] r: continue: sum: 90
+[  +0.100017] r: continue: sum: 90
+[  +0.100019] r: continue: sum: 90
+[  +0.100018] r: continue: sum: 135
+[  +0.100022] r: continue: sum: 135
+[  +0.100015] r: continue: sum: 135
+[  +0.100015] r: continue: sum: 135
+[  +0.100036] r: continue: sum: 135
+[  +0.100053] r: continue: sum: 135
+[  +0.100020] r: continue: sum: 135
+[  +0.100028] r: continue: sum: 135
+[  +0.100041] r: continue: sum: 135
+[  +0.100021] r: continue: sum: 135
+[  +0.096219] w: removing from cmap
+[  +0.000004] w: remove cmap: 0
+[  +0.000002] w: remove cmap: 5
+[  +0.000001] w: remove cmap: 2
+[  +0.000001] w: remove cmap: 9
+[  +0.000000] w: remove cmap: 5
+[  +0.000001] w: remove cmap: 2
+[  +0.000001] w: remove cmap: 8
+[  +0.000000] w: remove cmap: 3
+[  +0.000001] w: remove cmap: 1
+[  +0.000000] w: remove cmap: 7
+[  +0.000039] w: done
+[  +0.003755] r: done: sum == 0
+
+
+```
+
+# 07
+
+```shell
+$ sudo rmmod rcucmap
+```
+
+```shell
+[ +17.767446] rcucmap: deleting cmap
+[  +0.000007] rcucmap: exit
+
+```
\ No newline at end of file

diff --git a/krcu-cmap/README.md b/krcu-cmap/README.md
deleted file mode 100644 (file)
index 489fe5a..0000000
--- a/krcu-cmap/README.md
+++ /dev/null
@@ -1,194 +0,0 @@
-# krcu-cmap
-
-- source: [linuxyz/krcu-cmap](https://github.com/seantywork/linuxyz/tree/main/krcu-cmap)
-- date: 2509-24
-
-In user space on Linux, we can utilize `pthread_rwlock` to design a read-heavy data structure.
-
-A similar thing in the Linux kernel space is called `rcu`, a shorthand for "read, copy, update".
-
-Full documentation on it is [here](https://www.kernel.org/doc/html/next/RCU/whatisRCU.html)
-
-However, with `pthread_rwlock` in mind, it could be a little bit puzzling (at least it was for me) \
-to grasp the proper use and order of apis unlike in the case of \
-pthread_rwlock where you simply call *_rdlock on read and *_wrlock \
-on update
-
-Reading the docs wasn't enough for me.
-
-So I did the thing when I'm confused about the concept of multi-threading \
-and syncing mechanism: \
-**Building a concurrent map example!**
-
-Here, this is the outlay of this example.
-
-
-```shell
-# a regular old concurrent map...
-concurrent_map
-|     bucket_count
-|     bucket_0-------
-|     |     spin_lock      
-|     |     node_0----node_1----node_n
-|     bucket_1-------
-|     |     spin_lock
-|     |     node_0----node_1----node_n
-|     bucket_2-------
-|     |     spin_lock
-|     |     node_0----node_1----node_n
-|     bucket_n-------
-|     |     spin_lock
-|     |     node_0----node_1----node_n
-|     ----------------
-|     |
----------------
-```
-However, in this case, our `node` data structure here \
-contains the magic element
-
-```c
-struct node {
-    int key;
-    int value;
-       struct list_head _node; 
-       struct rcu_head _rcu; // <----- hello!
-};
-```
-
-With all these, our scenario will flow like the diagram below.
-The critical part to look for (in my opinion) is \
-`delete all nodes` part from writer thread.
-
-If this `rcu` thing cannot guarantee the basic functionality\
-we expect from things such as `pthread_rwlock`, then this part\
-will cause the GD kernel panic.
-
-```shell
-
-|---(r)eader thread------------|---(w)riter thread-----------|
-|    wait for cmap to be ready |                             |
-|                              |   create cmap               |
-|                              |   update cmap (fill up)     |
-|                              |   ready!                    |
-|                              |                             |
-|    read values from cmap     |   update cmap               |
-|    (interval 100ms)          |   (interval 1000ms)         |
-|    continue                  |   continue                  |
-|    continue                  |   continue                  |
-|    continue                  |   continue                  |
-|    continue                  |   delete all nodes          |
-|    continue...               |   exit                      |
-|    untile there is no value  |                             |
-|    (sum == 0)                |                             |
-|    exit                      |                             |
---------------------------------------------------------------
-```
-
-Now, let's compile the kernel module.
-
-```shell
-$ make
-```
-Pop up another terminal, and use `dmesg` command to follow.
-
-```shell
-
-$ sudo dmesg -wH
-```
-
-Load the kernel module with `insmod` command. \
-As soon as you do this, `dmesg` will output the result \
-described in the diagram above.
-
-```shell
-$ sudo insmod rcucmap.ko
-```
-
-```shell
-# `dmesg -wH` output
-[Sep24 09:06] r: init
-[  +0.000007] r: wait...
-[  +0.000087] w: init
-[  +0.000038] w: updating cmap
-[  +0.000003] w: update cmap: 0
-[  +0.000001] w: update cmap: 5
-[  +0.000001] w: update cmap: 2
-[  +0.000001] w: update cmap: 9
-[  +0.000001] w: update cmap: 5
-[  +0.000001] w: update cmap: 2
-[  +0.000000] w: update cmap: 8
-[  +0.000001] w: update cmap: 3
-[  +0.000001] w: update cmap: 1
-[  +0.000000] w: update cmap: 7
-[  +0.000001] w: ready
-[  +0.103514] r: run
-[  +0.000017] r: continue: sum: 45
-[  +0.100011] r: continue: sum: 45
-[  +0.100018] r: continue: sum: 45
-[  +0.100057] r: continue: sum: 45
-[  +0.100018] r: continue: sum: 45
-[  +0.100015] r: continue: sum: 45
-[  +0.100015] r: continue: sum: 45
-[  +0.100016] r: continue: sum: 45
-[  +0.100020] r: continue: sum: 45
-[  +0.100021] r: continue: sum: 45
-[  +0.100025] r: continue: sum: 45
-[  +0.100070] r: continue: sum: 45
-[  +0.100025] r: continue: sum: 45
-[  +0.100032] r: continue: sum: 45
-[  +0.100033] r: continue: sum: 45
-[  +0.100060] r: continue: sum: 45
-[  +0.100054] r: continue: sum: 45
-[  +0.100030] r: continue: sum: 45
-[  +0.100021] r: continue: sum: 45
-[  +0.100018] r: continue: sum: 90
-[  +0.100021] r: continue: sum: 90
-[  +0.100018] r: continue: sum: 90
-[  +0.100021] r: continue: sum: 90
-[  +0.100019] r: continue: sum: 90
-[  +0.100017] r: continue: sum: 90
-[  +0.100016] r: continue: sum: 90
-[  +0.100025] r: continue: sum: 90
-[  +0.100017] r: continue: sum: 90
-[  +0.100019] r: continue: sum: 90
-[  +0.100018] r: continue: sum: 135
-[  +0.100022] r: continue: sum: 135
-[  +0.100015] r: continue: sum: 135
-[  +0.100015] r: continue: sum: 135
-[  +0.100036] r: continue: sum: 135
-[  +0.100053] r: continue: sum: 135
-[  +0.100020] r: continue: sum: 135
-[  +0.100028] r: continue: sum: 135
-[  +0.100041] r: continue: sum: 135
-[  +0.100021] r: continue: sum: 135
-[  +0.096219] w: removing from cmap
-[  +0.000004] w: remove cmap: 0
-[  +0.000002] w: remove cmap: 5
-[  +0.000001] w: remove cmap: 2
-[  +0.000001] w: remove cmap: 9
-[  +0.000000] w: remove cmap: 5
-[  +0.000001] w: remove cmap: 2
-[  +0.000001] w: remove cmap: 8
-[  +0.000000] w: remove cmap: 3
-[  +0.000001] w: remove cmap: 1
-[  +0.000000] w: remove cmap: 7
-[  +0.000039] w: done
-[  +0.003755] r: done: sum == 0
-
-
-```
-
-As you can see, the program is working as expected and (thank god) \
-there is no kernel panic!
-
-Pleased, unload the kernel module.
-
-```shell
-$ sudo rmmod rcucmap
-```
-
-```shell
-[ +17.767446] rcucmap: deleting cmap
-[  +0.000007] rcucmap: exit
-
-```
\ No newline at end of file