Re: [libvirt] [PATCH 1/6] port allocator: make used port bitmap global

On 02/05/2018 02:21 PM, Daniel P. Berrangé wrote: > On Mon, Feb 05, 2018 at 02:11:24PM +0100, Peter Krempa wrote: >> On Mon, Feb 05, 2018 at 12:55:11 +0000, Daniel Berrange wrote: >>> On Mon, Feb 05, 2018 at 01:39:56PM +0100, Michal Privoznik wrote: >>>> On 02/01/2018 08:51 AM, Nikolay Shirokovskiy wrote: >>>>> >>>>> >>>>> On 29.01.2018 09:09, Michal Privoznik wrote: >>>>>> On 12/20/2017 07:35 AM, Nikolay Shirokovskiy wrote: >>>>>>> Host tcp4/tcp6 ports is a global resource thus we need to make >>>>>>> port accounting also global or we have issues described in [1] when >>>>>>> port allocator ranges of different instances are overlapped (which >>>>>>> is by default for qemu for example). >>>>>>> >>>>>>> Let's have only one global port allocator object that take care >>>>>>> of the entire ports range (0 - 65535) and introduce port range object >>>>>>> for clients to specify desired auto allocation band. >>>>>>> >>>>>>> [1] https://www.redhat.com/archives/libvir-list/2017-December/msg00600.html >>>>>>> --- >>>>>>> src/bhyve/bhyve_driver.c | 4 +- >>>>>>> src/bhyve/bhyve_utils.h | 2 +- >>>>>>> src/libvirt_private.syms | 3 +- >>>>>>> src/libxl/libxl_conf.c | 8 +-- >>>>>>> src/libxl/libxl_conf.h | 8 +-- >>>>>>> src/libxl/libxl_driver.c | 18 +++--- >>>>>>> src/qemu/qemu_conf.h | 6 +- >>>>>>> src/qemu/qemu_driver.c | 30 +++++----- >>>>>>> src/util/virportallocator.c | 125 ++++++++++++++++++++++++++++------------- >>>>>>> src/util/virportallocator.h | 20 ++++--- >>>>>>> tests/bhyvexml2argvtest.c | 6 +- >>>>>>> tests/libxlxml2domconfigtest.c | 8 +-- >>>>>>> tests/virportallocatortest.c | 48 ++++++++++------ >>>>>>> 13 files changed, 175 insertions(+), 111 deletions(-) >>>>>>> >>>>>> >>>>>>> diff --git a/src/util/virportallocator.c b/src/util/virportallocator.c >>>>>>> index fcd4f74..cd64356 100644 >>>>>>> --- a/src/util/virportallocator.c >>>>>>> +++ b/src/util/virportallocator.c >>>>>>> @@ -35,10 +35,14 @@ >>>>>>> >>>>>>> #define VIR_FROM_THIS VIR_FROM_NONE >>>>>>> >>>>>>> +typedef struct _virPortAllocator virPortAllocator; >>>>>>> +typedef virPortAllocator *virPortAllocatorPtr; >>>>>>> struct _virPortAllocator { >>>>>>> virObjectLockable parent; >>>>>>> virBitmapPtr bitmap; >>>>>>> +}; >>>>>>> >>>>>>> +struct _virPortRange { >>>>>>> char *name; >>>>>>> >>>>>>> unsigned short start; >>>>>>> @@ -48,6 +52,7 @@ struct _virPortAllocator { >>>>>>> }; >>>>>>> >>>>>>> static virClassPtr virPortAllocatorClass; >>>>>>> +static virPortAllocatorPtr virPortAllocatorInstance; >>>>>> >>>>>> I wonder if this is the way to go. I mean, this virPortAllocatorInstance >>>>>> is going to be a global variable that will never be freed (even if we >>>>>> wanted to). I mean, if virPortRange had a pointer to virPortAllocator >>>>> >>>>> Not sure why we need to free it. It is like global variables for classes, >>>>> we don't need to free them yet. As to libxlxml2domconfigtest it can be >>>>> fixed just like virportallocatortest by releasing all acquired ports. >>>> >>>> Well, okay. Disregard my suggestion. However, what we still need to >>>> discuss is the driver separation work of Daniel's. Dan, how badly will >>>> this hit you if I merged these? In another thread I suggested to turn >>>> this into a separate deaemon (which might be overkill). >>> >>> The caching of the used ports in the bitmap is just an optimization, to >>> avoid us having to retry the bind()+listen() on every port we've previously >>> got in use. If we split the daemon, if multiple daemons all need port >>> allocation tracking, they'll get separate virPortAllocator bitmap instances. >>> Since one daemon won't see what other daemon has in use, it will mean that >>> we must try to bind()+listen() on ports that the other daemon has in use. >>> Thereafter we'll have cached that usage the bitmap. >>> >>> The main downside is that if one daemon releases a port, the other daemon >>> won't see that release. This is only a significant problem if the 2 (or >>> more) daemons are using the same port range. This would, however, be >>> exactly the same when we have a per-QEMU instance daemon. The proposed >>> change, however, does not make life worse than it already is in this >>> respect. >>> >>> IOW, we'll probably have some trouble, but that's not a reason to reject >>> this proposal. It is just one of many things we'll need to figure out >>> wrt unique assignment. >> >> Well, you get slightly worse odds of having the same kind of race if you >> have multiple instances of the port allocation approach in multiple >> processes. >> >> Our problem is that when we bind()+listen() we still need to close that >> port and have qemu open it again. This race window is still present but >> will be worsened by multiple of these doing the same thing. >> >> When qemu will be able to accept the socket via FD passing then this >> would be strictly an optimization, but until then it worsens the odds of >> failure. > > I have patches to let QEMU accept a preopened FD for chardevs. > > VNC / SPICE are the other big ones we hit. I should make fixing those a > higher priority. Okay, so it looks like this can be merged. I mean, v2 can be merged (which fixes other issues raised like tests failing, build fixes in some drivers, etc.). Nikolay, do you think you can send v2?