Date: Fri, 6 May 2005 13:06:35 -0700 From: Kris Kennaway <kris@obsecurity.org> To: Kris Kennaway <kris@obsecurity.org> Cc: current@FreeBSD.org Subject: Re: Benchmarking mpsafevfs with parallel tarball extraction Message-ID: <20050506200635.GB79102@xor.obsecurity.org> In-Reply-To: <20050506184852.GA62656@xor.obsecurity.org> References: <20050506183529.GA46411@xor.obsecurity.org> <20050506184852.GA62656@xor.obsecurity.org>
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--0ntfKIWw70PvrIHh Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, May 06, 2005 at 11:48:52AM -0700, Kris Kennaway wrote: > On Fri, May 06, 2005 at 11:35:29AM -0700, Kris Kennaway wrote: >=20 > > I might be bumping into the bandwidth of md here - when I ran less > > rigorous tests with lower concurrency of extractions I seemed to be > > getting marginally better performance (about an effective concurrency > > of 2.2 for both 3 and 10 simultaneous extractions - so at least it > > doesn't seem to degrade badly). Or this might be reflecting VFS lock > > contention (which there is certainly a lot of, according to mutex > > profiling traces). >=20 > I suspect that I am hitting the md bandwidth: >=20 > # dd if=3D/dev/zero of=3D/dev/md0 bs=3D1024k count=3D500 > 500+0 records in > 500+0 records out > 524288000 bytes transferred in 9.501760 secs (55177988 bytes/sec) >=20 > which is a lot worse than I expected (even for a 400MHz CPU). >=20 > For some reason I get better performance writing to a filesystem > mounted on this md: >=20 > # dd if=3D/dev/zero of=3Dfoo bs=3D1024k count=3D500 > 500+0 records in > 500+0 records out > 524288000 bytes transferred in 7.943042 secs (66005946 bytes/sec) > # rm foo > # dd if=3D/dev/zero of=3Dfoo bs=3D1024k count=3D500 > 500+0 records in > 500+0 records out > 524288000 bytes transferred in 7.126929 secs (73564364 bytes/sec) > # rm foo > # dd if=3D/dev/zero of=3Dfoo bs=3D1024k count=3D500 > 500+0 records in > 500+0 records out > 524288000 bytes transferred in 7.237668 secs (72438804 bytes/sec) >=20 > If the write bandwidth is only 50-70MB/sec, then it won't be hard to > saturate, so I won't probe the full scalability of mpsafevfs here. I tried on a quad amd64 machine, which has md bandwidth an order of magnitude greater, but it has the same limiting concurrency of 2.2, so something else is happening here. Kris --0ntfKIWw70PvrIHh Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (FreeBSD) iD8DBQFCe85LWry0BWjoQKURAuxLAJ9MLa6JtgUOCGLTL72JTpGU0zN1JACZAUiI H7bHiPx4WcQ90qsZ3aUVxKo= =SjNl -----END PGP SIGNATURE----- --0ntfKIWw70PvrIHh--
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