Date: Fri, 9 Apr 2021 22:33:14 +0000 From: =?iso-8859-1?Q?Wei=DF=2C_Dr=2E_J=FCrgen?= <weiss@uni-mainz.de> To: 'Mark Johnston' <markj@freebsd.org>, Andriy Gapon <avg@freebsd.org> Cc: freebsd-stable List <stable@freebsd.org>, FreeBSD Current <current@freebsd.org> Subject: RE: stable/13, vm page counts do not add up Message-ID: <0ee7dc3d7bc7443b9ae60a833835caed@uni-mainz.de> In-Reply-To: <YG4ckaRbub6kEFO8@nuc> References: <0606571f-fec0-c7ad-98e8-a0b8554918e2@FreeBSD.org> <YG4OAVa0ohh4illU@nuc> <f509bf54-e283-eb29-2db2-1457dae7bc13@FreeBSD.org> <YG4ckaRbub6kEFO8@nuc>
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> -----Original Message----- > From: owner-freebsd-current@freebsd.org <owner-freebsd- > current@freebsd.org> On Behalf Of Mark Johnston > Sent: Wednesday, April 7, 2021 10:57 PM > To: Andriy Gapon <avg@freebsd.org> > Cc: freebsd-stable List <stable@freebsd.org>; FreeBSD Current > <current@freebsd.org> > Subject: Re: stable/13, vm page counts do not add up >=20 > On Wed, Apr 07, 2021 at 11:22:41PM +0300, Andriy Gapon wrote: > > On 07/04/2021 22:54, Mark Johnston wrote: > > > On Wed, Apr 07, 2021 at 10:42:57PM +0300, Andriy Gapon wrote: > > >> > > >> I regularly see that the top's memory line does not add up (and by a= lot). > > >> That can be seen with vm.stats as well. > > >> > > >> For example: > > >> $ sysctl vm.stats | fgrep count > > >> vm.stats.vm.v_cache_count: 0 > > >> vm.stats.vm.v_user_wire_count: 3231 > > >> vm.stats.vm.v_laundry_count: 262058 > > >> vm.stats.vm.v_inactive_count: 3054178 > > >> vm.stats.vm.v_active_count: 621131 > > >> vm.stats.vm.v_wire_count: 1871176 > > >> vm.stats.vm.v_free_count: 187777 > > >> vm.stats.vm.v_page_count: 8134982 > > >> > > >> $ bc > > >>>>> 187777 + 1871176 + 621131 + 3054178 + 262058 > > >> 5996320 > > >>>>> 8134982 - 5996320 > > >> 2138662 > > >> > > >> As you can see, it's not a small number of pages either. > > >> Approximately 2 million pages, 8 gigabytes or 25% of the whole memor= y > on this > > >> system. > > >> > > >> This is 47c00a9835926e96, 13.0-STABLE amd64. > > >> I do not think that I saw anything like that when I used (much) olde= r > FreeBSD. > > > > > > One relevant change is that vm_page_wire() no longer removes pages > from > > > LRU queues, so the count of pages in the queues can include wired > pages. > > > If the page daemon runs, it will dequeue any wired pages that are > > > encountered. > > > > Maybe I misunderstand how that works, but I would expect that the sum > of all > > counters could be greater than v_page_count at times. But in my case i= t's > less. >=20 > I misread, sorry. You're right, what I described would cause double > counting. >=20 > I don't know what might be causing it then. It could be a page leak. > The kernel allocates wired pages without adjusting the v_wire_count > counter in some cases, but the ones I know about happen at boot and > should not account for such a large disparity. I do not see it on a few > systems that I have access to. >=20 > > > This was done to reduce queue lock contention, operations like > > > sendfile() which transiently wire pages would otherwise trigger two > > > queue operations per page. Now that queue operations are batched thi= s > > > might not be as important. > > > > > > We could perhaps add a new flavour of vm_page_wire() which is not laz= y > > > and would be suited for e.g., the buffer cache. What is the primary > > > source of wired pages in this case? > > > > It should be ZFS, I guess. > > > > -- > > Andriy Gapon > _______________________________________________ > freebsd-current@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current- > unsubscribe@freebsd.org" I see kernel memory disappearing, when enabling ktls: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D253281 Last test done with 13.0-RC1.=20 I'm a bit at a loss how to debug this further. Regards=20 Juergen Weiss Juergen Weiss | weiss@uni-mainz.de |
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