From 491c6f1044630a4134393ef91df8bcf387ae5268 Mon Sep 17 00:00:00 2001
From: ilyam8 <ilya@netdata.cloud>
Date: Sun, 8 May 2022 18:08:49 +0300
Subject: consider only shrinkable ZFS ARC as cache on Linux

---
 linux/LinuxProcessList.c | 2 ++
 linux/Platform.c         | 9 +++++++--
 zfs/ZfsArcStats.h        | 1 +
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/linux/LinuxProcessList.c b/linux/LinuxProcessList.c
index 7a7e0a28..e799661a 100644
--- a/linux/LinuxProcessList.c
+++ b/linux/LinuxProcessList.c
@@ -1922,6 +1922,7 @@ static inline void LinuxProcessList_scanZfsArcstats(LinuxProcessList* lpl) {
 
       switch (buffer[0]) {
       case 'c':
+         tryRead("c_min", &lpl->zfs.min);
          tryRead("c_max", &lpl->zfs.max);
          tryReadFlag("compressed_size", &lpl->zfs.compressed, lpl->zfs.isCompressed);
          break;
@@ -1956,6 +1957,7 @@ static inline void LinuxProcessList_scanZfsArcstats(LinuxProcessList* lpl) {
 
    lpl->zfs.enabled = (lpl->zfs.size > 0 ? 1 : 0);
    lpl->zfs.size    /= 1024;
+   lpl->zfs.min    /= 1024;
    lpl->zfs.max    /= 1024;
    lpl->zfs.MFU    /= 1024;
    lpl->zfs.MRU    /= 1024;
diff --git a/linux/Platform.c b/linux/Platform.c
index d9c23394..38b66e83 100644
--- a/linux/Platform.c
+++ b/linux/Platform.c
@@ -358,8 +358,13 @@ void Platform_setMemoryValues(Meter* this) {
    this->values[4] = pl->availableMem;
 
    if (lpl->zfs.enabled != 0 && !Running_containerized) {
-      this->values[0] -= lpl->zfs.size;
-      this->values[3] += lpl->zfs.size;
+      // ZFS does not shrink below the value of zfs_arc_min.
+      unsigned long long int shrinkableSize = 0;
+      if (lpl->zfs.size > lpl->zfs.min)
+         shrinkableSize = lpl->zfs.size - lpl->zfs.min;
+      this->values[0] -= shrinkableSize;
+      this->values[3] += shrinkableSize;
+      this->values[4] += shrinkableSize;
    }
 }
 
diff --git a/zfs/ZfsArcStats.h b/zfs/ZfsArcStats.h
index e2cb4117..1fe72361 100644
--- a/zfs/ZfsArcStats.h
+++ b/zfs/ZfsArcStats.h
@@ -10,6 +10,7 @@ in the source distribution for its full text.
 typedef struct ZfsArcStats_ {
    int enabled;
    int isCompressed;
+   unsigned long long int min;
    unsigned long long int max;
    unsigned long long int size;
    unsigned long long int MFU;
-- 
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