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authorAmar Tumballi <amarts@redhat.com>2018-10-16 16:31:49 +0530
committerAmar Tumballi <amarts@redhat.com>2018-12-14 17:34:28 +0000
commitd49b41e817d592c1904b6f01716df6546dad3ebe (patch)
tree12546ad6da0534683cb7bed5b829500ecdfafe93 /tests/features/fuse-lru-limit.t
parentfc74ef85e0780e0a265275df00e4d0d4a2d05eab (diff)
fuse: add --lru-limit option
The inode LRU mechanism is moot in fuse xlator (ie. there is no limit for the LRU list), as fuse inodes are referenced from kernel context, and thus they can only be dropped on request of the kernel. This might results in a high number of passive inodes which are useless for the glusterfs client, causing a significant memory overhead. This change tries to remedy this by extending the LRU semantics and allowing to set a finite limit on the fuse inode LRU. A brief history of problem: When gluster's inode table was designed, fuse didn't have any 'invalidate' method, which means, userspace application could never ask kernel to send a 'forget()' fop, instead had to wait for kernel to send it based on kernel's parameters. Inode table remembers the number of times kernel has cached the inode based on the 'nlookup' parameter. And 'nlookup' field is not used by no other entry points (like server-protocol, gfapi etc). Hence the inode_table of fuse module always has to have lru-limit as '0', which means no limit. GlusterFS always had to keep all inodes in memory as kernel would have had a reference to it. Again, the reason for this is, kernel's glusterfs inode reference was pointer of 'inode_t' structure in glusterfs. As it is a pointer, we could never free it (to prevent segfault, or memory corruption). Solution: In the inode table, handle the prune case of inodes with 'nlookup' differently, and call a 'invalidator' method, which in this case is fuse_invalidate(), and it sends the request to kernel for getting the forget request. When the kernel sends the forget, it means, it has dropped all the reference to the inode, and it will send the forget with the 'nlookup' parameter too. We just need to make sure to reduce the 'nlookup' value we have when we get forget. That automatically cause the relevant prune to happen. Credits: Csaba Henk, Xavier Hernandez, Raghavendra Gowdappa, Nithya B fixes: bz#1560969 Change-Id: Ifee0737b23b12b1426c224ec5b8f591f487d83a2 Signed-off-by: Amar Tumballi <amarts@redhat.com>
Diffstat (limited to 'tests/features/fuse-lru-limit.t')
-rw-r--r--tests/features/fuse-lru-limit.t42
1 files changed, 42 insertions, 0 deletions
diff --git a/tests/features/fuse-lru-limit.t b/tests/features/fuse-lru-limit.t
new file mode 100644
index 0000000..9f12116
--- /dev/null
+++ b/tests/features/fuse-lru-limit.t
@@ -0,0 +1,42 @@
+#!/bin/bash
+
+. $(dirname $0)/../include.rc
+. $(dirname $0)/../volume.rc
+
+cleanup
+
+TEST glusterd
+TEST pidof glusterd
+TEST $CLI volume create $V0 $H0:$B0/${V0}{0,1}
+TEST $CLI volume start $V0
+TEST glusterfs -s $H0 --volfile-id $V0 $M0
+
+EXPECT "1" get_mount_active_size_value $V0 $M0
+EXPECT "0" get_mount_lru_size_value $V0 $M0
+
+mkdir ${M0}/dir-{1..9}
+for i in {1..9}; do
+ for j in {1..1000}; do
+ echo "Test file" > ${M0}/dir-$i/file-$j;
+ done;
+done
+lc=$(get_mount_lru_size_value $V0 ${M0})
+# ideally it should be 9000+
+TEST [ $lc -ge 9000 ]
+
+TEST umount $M0
+
+TEST glusterfs -s $H0 --volfile-id $V0 --lru-limit 1000 $M0
+
+TEST find $M0
+lc=$(get_mount_lru_size_value $V0 ${M0})
+# ideally it should be <1000
+# Not sure if there are any possibilities of buffer need.
+TEST [ $lc -le 1000 ]
+
+TEST rm -rf $M0/*
+
+EXPECT "1" get_mount_active_size_value $V0 $M0
+EXPECT "0" get_mount_lru_size_value $V0 $M0
+
+cleanup