Date: Mon, 26 Oct 2015 08:33:53 -0700 From: Adrian Chadd <adrian.chadd@gmail.com> To: Jia-Shiun Li <jiashiun@gmail.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: vmtotal consumes significant portion of cpu cycles Message-ID: <CAJ-Vmok3dcz_A_PLMZKs-bs34m2cdk8SrMAtaEgW4jv7pEVvnw@mail.gmail.com> In-Reply-To: <CAHNYxxOWqAZxt%2BZcjU_JnUhE5n7%2BCbwv-_6yTOy1bOaYS=Z4gw@mail.gmail.com> References: <CAHNYxxOWqAZxt%2BZcjU_JnUhE5n7%2BCbwv-_6yTOy1bOaYS=Z4gw@mail.gmail.com>
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hiya, yes, please do. I recall there's some global vm lock and big hash/list walk involved when vmtotal() is called. :( -a On 26 October 2015 at 06:28, Jia-Shiun Li <jiashiun@gmail.com> wrote: > Hi all, > > I noticed that 'sysctl -vm 1' consumes about 5% cpu time on a machine with > 2x 6-core Xeon E5v3 and 64GB memory. That's a lot for a monitoring tool. > > After digging a while I found that it is vmtotal() in kernel that consumes > major cycles. When memory usage is high the cost of vmtotal() rises too. It > is reproducible with sysctl when memory utilization is high: > > % time repeat 100 sysctl vm.vmtotal > /dev/null > 0.055u 8.102s 0:08.19 99.5% 31+175k 0+0io 0pf+0w > > % top > last pid: 40272; load averages: 0.32, 4.74, 8.01 up 3+01:19:54 > 17:23:59 > 58 processes: 1 running, 57 sleeping > CPU: 0.1% user, 0.0% nice, 1.6% system, 0.1% interrupt, 98.3% idle > Mem: 4509M Active, 52G Inact, 2819M Wired, 1572M Buf, 2930M Free > Swap: 3598M Total, 3598M Free > > PID USERNAME THR PRI NICE SIZE RES STATE C TIME CPU > COMMAND > 46841 root 30 20 0 9248M 7930M kqread 9 20.8H 11.88% bhyve > 49914 jsli 1 23 0 19320K 3884K select 5 134:08 4.79% systat > > > In FreeBSD source tree systat and vmstat are major user. Other tools like > bsnmpd may use it too via sysctl. > > I don't have idea yet how this can be improved. Shall I create a bug to > keep track of it? > > > -Jia-Shiun > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
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