Date: Wed, 26 Jan 2011 14:20:28 +0100 From: Bartosz Stec <bartosz.stec@it4pro.pl> To: John Baldwin <jhb@freebsd.org> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: top shows only half of realmem? Message-ID: <4D401F9C.6050402@it4pro.pl> In-Reply-To: <201101260806.10084.jhb@freebsd.org> References: <4D401192.3030400@it4pro.pl> <201101260806.10084.jhb@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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
And here's the part of /boot/loader.conf for ZFS tuning which may (or
probably may not) connected to this issue:
vm.kmem_size="1536M"
vm.kmem_size_max="1536M"
vfs.zfs.arc_max="1280M"
--
Bartosz Stec
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4D401F9C.6050402>