Date: Sun, 22 Jul 2012 09:19:13 +0200 (CEST) From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> To: Richard Yao <ryao@gentoo.org> 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: <alpine.BSF.2.00.1207220916030.3912@wojtek.tensor.gdynia.pl> In-Reply-To: <500B795B.7000307@gentoo.org> 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> <500B795B.7000307@gentoo.org>
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> You are right. It is not capped at that speed: > > root@freebsd:/root # dd if=/dev/zero of=/dev/da1 bs=16384 count=262144 > > > > 262144+0 records in > 262144+0 records out > 4294967296 bytes transferred in 615.840721 secs (6974153 bytes/sec) > > you did test da1 while dmesg are about da0? is it OK and da1 is another qemu-kvm vdisk? If so, check dd if=/dev/zero of=/dev/da1 bs=512 count=256k and compare speed. i bet at something near 250kB/s and i think it is long I/O service pathlength in qemu-kvm SCSI device simulator. Just my bet i don't run FreeBSD on any VM (as opposed to running Windows under FreeBSD in VBox) check out how much CPU is used on the host side when you do that test.
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