File 27cd7635-increase-daemons-file-limit.patch of Package libvirt.6751

commit 27cd76350021d36b9bd8b187ce5c8919659e3806
Author: Daniel P. Berrange <berrange@redhat.com>
Date:   Wed Mar 15 16:51:51 2017 +0000

    Increase default file handle limits for daemons
    
    Linux still defaults to a 1024 open file handle limit. This causes
    scalability problems for libvirtd / virtlockd / virtlogd on large
    hosts which might want > 1024 guest to be running. In fact if each
    guest needs > 1 FD, we can't even get to 500 guests. This is not
    good enough when we see machines with 100's of physical cores and
    TBs of RAM.
    
    In comparison to other memory requirements of libvirtd & related
    daemons, the resource usage associated with open file handles
    is essentially line noise. It is thus reasonable to increase the
    limits unconditionally for all installs.
    
    Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

Index: libvirt-2.0.0/daemon/libvirtd.service.in
===================================================================
--- libvirt-2.0.0.orig/daemon/libvirtd.service.in
+++ libvirt-2.0.0/daemon/libvirtd.service.in
@@ -23,8 +23,11 @@ ExecStart=@sbindir@/libvirtd $LIBVIRTD_A
 ExecReload=/bin/kill -HUP $MAINPID
 KillMode=process
 Restart=on-failure
-# Override the maximum number of opened files
-#LimitNOFILE=2048
+# At least 1 FD per guest, often 2 (eg qemu monitor + qemu agent).
+# eg if we want to support 4096 guests, we'll typically need 8192 FDs
+# If changing this, also consider virtlogd.service & virtlockd.service
+# limits which are also related to number of guests
+LimitNOFILE=8192
 
 [Install]
 WantedBy=multi-user.target
Index: libvirt-2.0.0/src/locking/virtlockd.service.in
===================================================================
--- libvirt-2.0.0.orig/src/locking/virtlockd.service.in
+++ libvirt-2.0.0/src/locking/virtlockd.service.in
@@ -12,6 +12,10 @@ ExecReload=/bin/kill -USR1 $MAINPID
 # cause the machine to be fenced (rebooted), so make
 # sure we discourage OOM killer
 OOMScoreAdjust=-900
+# Needs to allow for max guests * average disks per guest
+# libvirtd.service written to expect 4096 guests, so if we
+# allow for 4 disks per guest, we get:
+LimitNOFILE=16384
 
 [Install]
 Also=virtlockd.socket
Index: libvirt-2.0.0/src/logging/virtlogd.service.in
===================================================================
--- libvirt-2.0.0.orig/src/logging/virtlogd.service.in
+++ libvirt-2.0.0/src/logging/virtlogd.service.in
@@ -13,6 +13,11 @@ ExecReload=/bin/kill -USR1 $MAINPID
 # cause the machine to be fenced (rebooted), so make
 # sure we discourage OOM killer
 OOMScoreAdjust=-900
+# Need to have at least one file open per guest (eg QEMU
+# stdio log), but might be more (eg serial console logs)
+# libvirtd.service written to expect 4096 guests, so if we
+# guess at 2 log files per guest here (stdio + 1 serial):
+LimitNOFILE=8192
 
 [Install]
 Also=virtlogd.socket