[PATCH] isar-bootstrap: Increase cache room

[Alexander Smirnov <asmirnov@ilbers.de>]

According to the man page for 'apt.conf', there are three variables:
 - Cache-Start: initial size of mmap cache room
 - Cache-Grow: gap for dynamic mmap cache growth
 - Cache-Limit: maximal cache size after growth

If dynamic resize of mmap region is not avaialbe, the apt uses
pre-allocated Cache-Start room [1] for mmap file.

Building Isar on one of the Debian host with kernel 3.4, I got the
following problem for 'qemuarm64-stretch' configuration:

8<--
Hit:1 http://security.debian.org stretch/updates InRelease
Ign:2 http://ftp.de.debian.org/debian stretch InRelease
Hit:3 http://ftp.de.debian.org/debian stretch-updates InRelease
Hit:4 http://ftp.de.debian.org/debian stretch Release
E: Dynamic MMap ran out of room. Please increase the size of APT::Cache-Start. Current value: 25165824. (man 5 apt.conf)
qemu: uncaught target signal 11 (Segmentation fault) - core dumped
Segmentation fault
8<--

I have no information, why exactly the room could not be re-sized on this
system, but it would be better to increase the initial room size for apt.
This patch increases the default apt cache twice.

Signed-off-by: Alexander Smirnov <asmirnov@ilbers.de>
---
 meta/recipes-core/isar-bootstrap/isar-bootstrap.bb | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/meta/recipes-core/isar-bootstrap/isar-bootstrap.bb b/meta/recipes-core/isar-bootstrap/isar-bootstrap.bb
index a38dd88..4cdefaa 100644
--- a/meta/recipes-core/isar-bootstrap/isar-bootstrap.bb
+++ b/meta/recipes-core/isar-bootstrap/isar-bootstrap.bb
@@ -187,7 +187,9 @@ do_apt_update() {
 
     E="${@bb.utils.export_proxies(d)}"
     export DEBIAN_FRONTEND=noninteractive
-    sudo -E chroot "${ROOTFSDIR}" /usr/bin/apt-get update -y
+    sudo -E chroot "${ROOTFSDIR}" /usr/bin/apt-get update -y \
+                                      -o APT::Cache-Start=50331648
+                                     
     sudo -E chroot "${ROOTFSDIR}" /usr/bin/apt-get dist-upgrade -y \
                                       -o Debug::pkgProblemResolver=yes
 }
-- 
2.1.4