-use strict;
-use Test::More;
-use File::Temp qw(tempfile);
-use PublicInbox::TestCommon;
-use PublicInbox::Spawn qw(which);
-use_ok 'PublicInbox::NDC_PP';
+use strict; use v5.10.1; use PublicInbox::TestCommon;
+use File::Temp 0.19;
+use_ok 'PublicInbox::Syscall';
+
+# btrfs on Linux is copy-on-write (COW) by default. As of Linux 5.7,
+# this still leads to fragmentation for SQLite and Xapian files where
+# random I/O happens, so we disable COW just for SQLite files and Xapian
+# directories. Disabling COW disables checksumming, so we only do this
+# for regeneratable files, and not canonical git storage (git doesn't
+# checksum refs, only data under $GIT_DIR/objects).