Re: [libvirt] [PATCH v2] qemu: add a max_core setting to qemu.conf for core dump size
On Tue, Jul 12, 2016 at 11:38:22AM +0200, Martin Kletzander wrote:
On Tue, Jul 12, 2016 at 10:12:36AM +0100, Daniel P. Berrange wrote:
> Currently the QEMU processes inherit their core dump rlimit
> from libvirtd, which is really suboptimal. This change allows
> their limit to be directly controller from qemu.conf instead.
> ---
>
> Changed in v2:
>
> - Allow use of string "unlimited"
>
> src/libvirt_private.syms | 2 ++
> src/qemu/libvirtd_qemu.aug | 1 +
> src/qemu/qemu.conf | 16 +++++++++++++++-
> src/qemu/qemu_conf.c | 17 +++++++++++++++++
> src/qemu/qemu_conf.h | 1 +
> src/qemu/qemu_process.c | 1 +
> src/qemu/test_libvirtd_qemu.aug.in | 1 +
> src/util/vircommand.c | 14 ++++++++++++++
> src/util/vircommand.h | 1 +
> src/util/virprocess.c | 36 ++++++++++++++++++++++++++++++++++++
> src/util/virprocess.h | 1 +
> 11 files changed, 90 insertions(+), 1 deletion(-)
>
[...]
> diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
> index 8bc23ba..a8edc2b 100644
> --- a/src/qemu/libvirtd_qemu.aug
> +++ b/src/qemu/libvirtd_qemu.aug
> @@ -72,6 +72,7 @@ module Libvirtd_qemu =
> | bool_entry "set_process_name"
> | int_entry "max_processes"
> | int_entry "max_files"
> + | int_entry "max_core"
This should be expanded to allow "unlimited" as well.
Opps, yes.
> diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
> index 510cd9a..b730202 100644
> --- a/src/qemu/qemu_conf.h
> +++ b/src/qemu/qemu_conf.h
> @@ -148,6 +148,7 @@ struct _virQEMUDriverConfig {
>
> unsigned int maxProcesses;
> unsigned int maxFiles;
> + unsigned long long maxCore;
>
This is not initialized anywhere, effectively making the limit default
to 0 IIUC.
Yes, that's correct as per the qemu.conf docs - we don't allow
core dumps by default, since they can be absolutely massive
and so have a significant impact on the host OS in terms of time
& I/O bandwidth required to dump the guest, as well as disk space
usage. So core dumps are an opt-in thing.
> diff --git a/src/util/virprocess.c b/src/util/virprocess.c
> index 09dd3c9..2b71445 100644
> --- a/src/util/virprocess.c
> +++ b/src/util/virprocess.c
> @@ -914,6 +914,42 @@ virProcessSetMaxFiles(pid_t pid ATTRIBUTE_UNUSED, unsigned int
files)
> }
> #endif /* ! (HAVE_SETRLIMIT && defined(RLIMIT_NOFILE)) */
>
> +#if HAVE_SETRLIMIT && defined(RLIMIT_CORE)
> +int
> +virProcessSetMaxCoreSize(pid_t pid, unsigned long long bytes)
> +{
> + struct rlimit rlim;
> +
> + rlim.rlim_cur = rlim.rlim_max = bytes;
Shouldn't be this set to RLIM_INFINITY if "unlimited" was requested?
Not taht ULLONG_MAX would not be enough, it's just that it's rlim_t and
it would be nicer to use it as described.
IIUC, you're effectively saying that we should do
if (bytes == ULLONG_MAX)
rlim_max = RLIM_INFINITY;
else
rlim_max = bytes;
RLIM_INFINITY is just an integer constant - if that's not the same
as ULONG_MAX, then we ought to deal with that right up front a time
of parsing in QEMU. eg add a virConfGetValueRLin() that returns an
rlim_t value so we get range checking.
Regards,
Daniel
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