freebsd: Support laundry memory and ZFS ARC

FreeBSD 11.1 removes cache memory and adds laundry memory. The MIB of
cache memory still exists, but its value is always set to zero.
According to the man page of top(1), the value of laundry memory means
number of dirty pages queued for laundering, suggesting that it should
be added to the 'user' in libgtop because it cannot be freed immediately
without writing out data. Laundry memory was part of inactive memory in
older FreeBSD releases.

FreeBSD systems running on ZFS usually have a large portion of memory
used as ZFS ARC, which has similar purpose to buffer cache of other
filesystems. ZFS ARC can usually be freed quickly when the system needs
more memory, so we don't want to put it in 'user' in libgtop. However,
both buffer cache and ZFS ARC are parts of wired memory, and wired
memory is counted in 'user'. Therefore, we subtract the size of ZFS ARC
from wired memory when calculating 'user' value, making it more useful
to FreeBSD users.

This patch is based on the patch submiited three years ago by
Benoît Dejean <bdejean@gmail.com>.

https://bugzilla.gnome.org/show_bug.cgi?id=748928
https://gitlab.gnome.org/GNOME/libgtop/issues/31

1 files changed, 18 insertions, 2 deletions

diff --git a/sysdeps/freebsd/mem.c b/sysdeps/freebsd/mem.c
index 22f560ed..fa7e86b6 100644
--- a/sysdeps/freebsd/mem.c
+++ b/sysdeps/freebsd/mem.c
@@ -55,6 +55,16 @@ static gulong mem_get_by_bytes (glibtop *server, const char *name) {
 	return result;
 }
 
+static gulong try_mem_get_by_bytes (glibtop *server, const char *name) {
+	gulong result = 0;
+	size_t len = sizeof (result);
+
+	if (sysctlbyname (name, &result, &len, NULL, 0)) {
+		return 0;
+	}
+	return result;
+}
+
 static gulong mem_get_by_pages (glibtop *server, const char *name) {
 	guint result = 0;
 	size_t len = sizeof (result);
@@ -71,29 +81,35 @@ glibtop_get_mem_s (glibtop *server, glibtop_mem *buf)
 	gulong memtotal;
 	gulong memactive;
 	gulong meminactive;
+	gulong memlaundry;
 	gulong memwired;
 	gulong memcached;
 	gulong membuffer;
 	gulong memfree;
+	gulong zfs_arc_size;
 
 	memset (buf, 0, sizeof *buf);
 
 	memtotal = mem_get_by_bytes (server, "hw.physmem");
 	memactive = mem_get_by_pages (server, "vm.stats.vm.v_active_count");
 	meminactive = mem_get_by_pages (server, "vm.stats.vm.v_inactive_count");
+	memlaundry = mem_get_by_pages (server, "vm.stats.vm.v_laundry_count");
 	memwired = mem_get_by_pages (server, "vm.stats.vm.v_wire_count");
 	memcached = mem_get_by_pages (server, "vm.stats.vm.v_cache_count");
 	membuffer = mem_get_by_bytes (server, "vfs.bufspace");
 	memfree = mem_get_by_pages (server, "vm.stats.vm.v_free_count");
 
+	zfs_arc_size = try_mem_get_by_bytes (server, "kstat.zfs.misc.arcstats.size");
+
 	buf->total = memtotal;
 	buf->used = memtotal - memfree;
 	buf->free = memfree;
 	buf->shared = 0;
 	buf->buffer = membuffer;
-	buf->cached = memcached;
+	buf->cached = memcached + zfs_arc_size;
 	buf->locked = 0;
 
-	buf->user = memactive + memwired;
+	buf->user = memactive + memlaundry + memwired - zfs_arc_size;
+
 	buf->flags = _glibtop_sysdeps_mem;
 }