Date: Thu, 27 Jan 2011 14:54:57 +0100 From: Bartosz Stec <bartosz.stec@it4pro.pl> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: freebsd-stable@freebsd.org Subject: Re: top shows only part of available physmem Message-ID: <4D417931.1060009@it4pro.pl> In-Reply-To: <20110127032142.GA19946@icarus.home.lan> References: <4D401192.3030400@it4pro.pl> <201101261235.56856.jhb@freebsd.org> <20110126180402.GA17271@tolstoy.tols.org> <201101261344.50756.jhb@freebsd.org> <4D40C355.6070306@it4pro.pl> <20110127032142.GA19946@icarus.home.lan>
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W dniu 2011-01-27 04:21, Jeremy Chadwick pisze: > On Thu, Jan 27, 2011 at 01:59:01AM +0100, Bartosz Stec wrote: >> W dniu 2011-01-26 19:44, John Baldwin pisze: >>> On Wednesday, January 26, 2011 1:04:02 pm Marco van Tol wrote: >>>> On Wed, Jan 26, 2011 at 12:35:56PM -0500, John Baldwin wrote: >>>>> On Wednesday, January 26, 2011 8:20:28 am Bartosz Stec wrote: >>>>>> W dniu 2011-01-26 14:06, John Baldwin pisze: >>>>>>> On Wednesday, January 26, 2011 7:20:34 am Bartosz Stec wrote: >>>>>>>> Guys, >>>>>>>> >>>>>>>> could someone explain me this? >>>>>>>> >>>>>>>> # sysctl hw.realmem >>>>>>>> hw.realmem: 2139029504 >>>>>>>> >>>>>>>> top line shows: >>>>>>>> >>>>>>>> Mem: 32M Active, 35M Inact, 899M Wired, 8392K Cache, 199M Buf, 58M Free >>>>>>>> >>>>>>>> 32+35+899+8+199+58 = 1231MB >>>>>>>> >>>>>>>> Shouldn't that sum to all available ram? Or maybe I'm reading it wrong? >>>>>>>> This machine has indeed 2GB of ram on board and showed in BIOS. >>>>>>>> i386 FreeBSD 8.2-PRERELEASE #16: Mon Jan 17 22:28:53 CET 2011 >>>>>>>> Cheers. >>>>>>> First, don't include 'buf' as isn't a separate set of RAM, it is only a range >>>>>>> of the virtual address space in the kernel. It used to be relevant when the >>>>>>> buffer cache was separate from the VM page cache, but now it is mostly >>>>>>> irrelevant (arguably it should just be dropped from top output). >>>>>> Thanks for the explanation. So 1231MB - 199MB Buf and we got about 1GB >>>>>> of memory instead of 2B. >>>>>> >>>>>>> However, look at what hw.physmem says (and the realmem and availmem lines in >>>>>>> dmesg). realmem is actually not that useful as it is not a count of the >>>>>>> amount of memory, but the address of the highest memory page available. There >>>>>>> can be less memory available than that due to "holes" in the address space for >>>>>>> PCI memory BARs, etc. >>>>>>> >>>>>> OK, here you go: >>>>>> # sysctl hw | grep mem >>>>>> >>>>>> hw.physmem: 2125893632 >>>>>> hw.usermem: 1212100608 >>>>>> hw.realmem: 2139029504 >>>>>> hw.pci.host_mem_start: 2147483648 >>>>> Humm, you should still have 2GB of RAM then. All the memory you set aside >>>>> for ARC should be counted in the 'wired' count, so I'm not sure why you see >>>>> 1GB of RAM rather than 2GB. >>>> For what its worth (seems to be the same values top shows), the sysctl's >>>> I use to make cacti graphs of memory usage are: (Counts are in pages) >>>> >>>> vm.stats.vm.v_page_size >>>> >>>> vm.stats.vm.v_wire_count >>>> vm.stats.vm.v_active_count >>>> vm.stats.vm.v_inactive_count >>>> vm.stats.vm.v_cache_count >>>> vm.stats.vm.v_free_count >>>> >>>> Using the output of those sysctls I allways get a cacti graph which at >>>> least very much seems to account for all memory, and has a flat surface >>>> in a stacked graph. >>> These sysctls are exactly what top uses. There is also a 'v_page_count' >>> which is a total count of pages. >>> >> So here's additional sysctl output from now: >> >> fbsd# sysctl hw | grep mem >> hw.physmem: 2125893632 >> hw.usermem: 1392594944 >> hw.realmem: 2139029504 >> hw.pci.host_mem_start: 2147483648 >> >> fbsd# sysctl vm.stats.vm >> vm.stats.vm.v_kthreadpages: 0 >> vm.stats.vm.v_rforkpages: 0 >> vm.stats.vm.v_vforkpages: 1422927 >> vm.stats.vm.v_forkpages: 4606557 >> vm.stats.vm.v_kthreads: 40 >> vm.stats.vm.v_rforks: 0 >> vm.stats.vm.v_vforks: 9917 >> vm.stats.vm.v_forks: 30429 >> vm.stats.vm.v_interrupt_free_min: 2 >> vm.stats.vm.v_pageout_free_min: 34 >> vm.stats.vm.v_cache_max: 27506 >> vm.stats.vm.v_cache_min: 13753 >> vm.stats.vm.v_cache_count: 20312 >> vm.stats.vm.v_inactive_count: 18591 >> vm.stats.vm.v_inactive_target: 20629 >> vm.stats.vm.v_active_count: 1096 >> vm.stats.vm.v_wire_count: 179027 >> vm.stats.vm.v_free_count: 6193 >> vm.stats.vm.v_free_min: 3260 >> vm.stats.vm.v_free_target: 13753 >> vm.stats.vm.v_free_reserved: 713 >> vm.stats.vm.v_page_count: 509752 >> vm.stats.vm.v_page_size: 4096 >> vm.stats.vm.v_tfree: 196418851 >> vm.stats.vm.v_pfree: 2837177 >> vm.stats.vm.v_dfree: 0 >> vm.stats.vm.v_tcached: 1305893 >> vm.stats.vm.v_pdpages: 3527455 >> vm.stats.vm.v_pdwakeups: 187 >> vm.stats.vm.v_reactivated: 83786 >> vm.stats.vm.v_intrans: 3053 >> vm.stats.vm.v_vnodepgsout: 134384 >> vm.stats.vm.v_vnodepgsin: 29213 >> vm.stats.vm.v_vnodeout: 96249 >> vm.stats.vm.v_vnodein: 29213 >> vm.stats.vm.v_swappgsout: 19730 >> vm.stats.vm.v_swappgsin: 8573 >> vm.stats.vm.v_swapout: 5287 >> vm.stats.vm.v_swapin: 2975 >> vm.stats.vm.v_ozfod: 83338 >> vm.stats.vm.v_zfod: 2462557 >> vm.stats.vm.v_cow_optim: 330 >> vm.stats.vm.v_cow_faults: 1239253 >> vm.stats.vm.v_vm_faults: 5898471 >> >> fbsd# sysctl vm.vmtotal >> vm.vmtotal: >> System wide totals computed every five seconds: (values in kilobytes) >> =============================================== >> Processes: (RUNQ: 1 Disk Wait: 0 Page Wait: 0 Sleep: 60) >> Virtual Memory: (Total: 4971660K Active: 699312K) >> Real Memory: (Total: 540776K Active: 29756K) >> Shared Virtual Memory: (Total: 41148K Active: 19468K) >> Shared Real Memory: (Total: 4964K Active: 3048K) >> Free Memory Pages: 105308K >> >> >> /usr/bin/top line: Mem: 4664K Active, 73M Inact, 700M Wired, 79M >> Cache, 199M Buf, 23M Free >> Sum (Without Buf): 879,5 MB >> >> So what are we looking at? Wrong sysctls/top output or maybe >> actually FreeBSD doesn't use all available RAM for some reason? >> Could it be hardware problem? Maybe I should provide some additional >> data? > Does the behaviour become more expected if you remove ZFS from the > picture? Please try this (yes really). > About an hour ago I had to hard reset this machine because it stopped responding (bu still gived ping response) after massive slowdown seen by SAMBA users. Now top shows following: Mem: 78M Active, 83M Inact, 639M Wired, 120K Cache, 199M Buf, 1139M Free. What I am afraid is that this PC slowly eats own memory and finally starved itself to death, because it happened second time in 2 weeks, and it seems that rebuilding world+kernel Mon Jan 17 22:28:53 CET 2011 could be the cause. For some strange reason I believe that Jeremy Chadwick could be right pointing ZFS. Way this machine stops responding without any info in logs makes me believe that it has simply lost ability to I/O to HDD (system is ZFS-only). -- Bartosz Stec
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