Date: Sat, 31 Mar 2018 19:31:13 -0700 From: Mark Millard <marklmi26-fbsd@yahoo.com> To: Andriy Gapon <avg@FreeBSD.org> Cc: freebsd-current@freebsd.org Subject: Re: Strange ARC/Swap/CPU on yesterday's -CURRENT Message-ID: <E41D1122-9E08-41C7-B970-AC085CC5829D@yahoo.com> In-Reply-To: <a1d97a3c-247f-8eb0-6497-d0273773741c@FreeBSD.org> References: <FD75495D-AC03-4037-9C62-5A3AC588317C@yahoo.com> <alpine.BSF.2.21.1803111759150.1232@desktop> <20180317103915.081ca2dd@thor.intern.walstatt.dynvpn.de> <F48580A7-2C4C-4297-B083-B7EEBA1C8665@yahoo.com> <f48d7287-c707-369d-f2cb-6bf0ed1054c6@FreeBSD.org> <D9288EC1-624E-4977-BD97-557DA11A5D8E@yahoo.com> <a1d97a3c-247f-8eb0-6497-d0273773741c@FreeBSD.org>
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On 2018-Mar-17, at 11:26 AM, Andriy Gapon <avg at FreeBSD.org> wrote: > On 17/03/2018 18:51, Mark Millard wrote: >> I'll note that top was a -w that reports: >> >> -w Display approximate swap usage for each process. > > As far as I can tell, this option is quite broken. > The "approximate swap usage" it reports is nowhere like it. I have a hypothesis for part of what top is counting in the process/thread SWAP column that might not be what one would expect. It appears to me that vnode-backed pages are being re-classfied sometimes for inactive processes, and this classification leads to top classifying the pages as not-resident but swapped (in that a "VN PAGER in" would be required, in systat -vmstat terms). Supporting details, if you care, otherwise skip the below: The hypothesis is from observing various hours of over 20 hours of poudriere-devel "bulk -a" activity, for which, at that point: vm.stats.vm.v_swappgsout: 0 vm.stats.vm.v_swappgsin: 0 vm.stats.vm.v_swapout: 0 vm.stats.vm.v_swapin: 0 vm.stats.vm.v_vnodepgsout: 6996 vm.stats.vm.v_vnodepgsin: 32641833 vm.stats.vm.v_vnodeout: 1030 vm.stats.vm.v_vnodein: 4305027 Sometimes top showed lots of wait/select/pause and such with positive SWAP and (mostly) 0K RES. Most of the processes were in the "wait" STATE. At other times, more like between 1 and 2 dozen had positive SWAP. There would be sudden large jumps in the number of such processes. Then over time it would decrease as the processes quit waiting (children process trees finished). The large jumps were not tied to Free becoming small or anything else obvious from what I was looking at. But the Free figure would increase at that time. For example, I recently saw such a large jump that was associated with Free increasing from "90G" as shown in top. (Much of the time there were between, say, 170 and 300 sleeping processes.) The context was under Hyper-V with 29 logical processors assigned to FreeBSD on a machine with 16 cores/32 threads and 114 GiBytes of RAM assigned to FreeBSD (of 128 GiBytes) and 256 GiBytes of swap-partition set up. PARALLEL_JOBS allowed the 29 and ALLOW_MAKE_JOBS was in use (allowing a potential for 29*29=841 or so running processes via poudriere bulk). For reference: at 25 hours-in [idle] had 148.3H (around 20% of the 29 threads * 25 H/thread) and [bufdaemon] had 48.9H (around 6.7%). [kernel] showed around 13.6H (817 min converted) and [pagedaemon] showed around 1.7H (101 min converted). Other processes had less TIME than any of these. === Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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