Re: [libvirt] [PATCH] Increase default file handle limits for daemons

Hi, On Wed, Mar 15, 2017 at 04:55:04PM +0000, Daniel P. Berrange wrote: > 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(a)redhat.com&gt; > --- > daemon/libvirtd.service.in | 7 +++++-- > src/locking/virtlockd.service.in | 4 ++++ > src/logging/virtlogd.service.in | 5 +++++ > 3 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/daemon/libvirtd.service.in b/daemon/libvirtd.service.in > index c72dde5..22fc156 100644 > --- a/daemon/libvirtd.service.in > +++ b/daemon/libvirtd.service.in > @@ -24,8 +24,11 @@ ExecStart=@sbindir@/libvirtd $LIBVIRTD_ARGS > 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). > +# If we want to support 2048 guests, we'll typically need 4096 FDs 4096 FDs here…

> +# If changing this, also consider virtlogd.service & virtlockd.service > +# limits which are also related to number of guests > +LimitNOFILE=8192 …but 8192 here. So we're looking at 4096 rather than 2048 guests (2 fds per guest)? > > [Install] > WantedBy=multi-user.target > diff --git a/src/locking/virtlockd.service.in b/src/locking/virtlockd.service.in > index 69b568f..c369591 100644 > --- a/src/locking/virtlockd.service.in > +++ b/src/locking/virtlockd.service.in > @@ -13,6 +13,10 @@ 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 Correct if we're looking at 4095 guests above. > > [Install] > Also=virtlockd.socket > diff --git a/src/logging/virtlogd.service.in b/src/logging/virtlogd.service.in > index 09e0740..be039c6 100644 > --- a/src/logging/virtlogd.service.in > +++ b/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 2048 guests, so if we Rather 4096 as above?

> +# guess at 2 log files per guest here (stdio + 1 serial): > +LimitNOFILE=8192 > > [Install] > Also=virtlogd.socket