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Date:      Sat, 21 Jul 2012 23:54:03 -0400
From:      Richard Yao <ryao@gentoo.org>
To:        Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
Cc:        Adrian Chadd <adrian@freebsd.org>, "hackers@FreeBSD.org" <hackers@freebsd.org>, current@freebsd.org, ivoras@freebsd.org
Subject:   Re: Awful FreeBSD 9 block IO performance in KVM
Message-ID:  <500B795B.7000307@gentoo.org>
In-Reply-To: <alpine.BSF.2.00.1207211014481.1535@wojtek.tensor.gdynia.pl>
References:  <50085193.6030203@gentoo.org> <CAJ-VmonynbAq8XaV_-dM7aEpQ1p33P3vHA1TMjsDs=ipXOsoTw@mail.gmail.com> <5009DB2A.7070408@gentoo.org> <500A13A6.7030503@gentoo.org> <alpine.BSF.2.00.1207211014481.1535@wojtek.tensor.gdynia.pl>

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On 07/21/2012 04:15 AM, Wojciech Puchar wrote:
>> da0: <QEMU QEMU HARDDISK 1.1.> Fixed Direct Access SCSI-5 device
>> da0: 3.300MB/s transfers
>> da0: Command Queueing enabled
>> da0: 409600MB (838860800 512 byte sectors: 255H 63S/T 52216C)
>>
>> It does not explain why virtio is slow though, although I still need t=
o
>> test virtio against the latest code. I will do ivan's raw block test
>> against virtio-blk, mainly because there is no point in doing it again=
st
>> a device whose transfers have been capped to 3.3MB/sec.
> are you sure it is really capped?
> i am not. just emulated sym device reports low speed.
> _______________________________________________
> freebsd-hackers@freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.o=
rg"

You are right. It is not capped at that speed:

root@freebsd:/root # dd if=3D/dev/zero of=3D/dev/da1 bs=3D16384 count=3D2=
62144



262144+0 records in
262144+0 records out
4294967296 bytes transferred in 615.840721 secs (6974153 bytes/sec)


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