From: Ingo Molnar <mingo@elte.hu>
To: Pekka Enberg <penberg@kernel.org>
Cc: Kevin Wolf <kwolf@redhat.com>,
kvm@vger.kernel.org, Asias He <asias.hejun@gmail.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Prasad Joshi <prasadjoshi124@gmail.com>,
Sasha Levin <levinsasha928@gmail.com>
Subject: Re: [PATCH 0/9] kvm tools, qcow: Improve QCOW performance
Date: Mon, 11 Jul 2011 12:36:45 +0200 [thread overview]
Message-ID: <20110711103645.GA11338@elte.hu> (raw)
In-Reply-To: <CAOJsxLFX5sLRtVfD4hoAx6h+0Pdd8SEXa=5MgOKiGrfdk9NCdQ@mail.gmail.com>
* Pekka Enberg <penberg@kernel.org> wrote:
> > As Ingo already said, the cache mode is probably the major
> > difference. From what I can see in your code, cache=writeback
> > would be the equivalent for what tools/kvm is doing, however
> > cache=none (i.e. O_DIRECT) is what people usually do with qemu.
>
> Yup, I posted 'cache=writeback' results too which are much closer
> to tools/kvm numbers.
tools/kvm/ seems to be about 20% faster on average:
511229952 bytes (511 MB) copied, 7.68312 s, 66.5 MB/s
511229952 bytes (511 MB) copied, 7.54065 s, 67.8 MB/s
511229952 bytes (511 MB) copied, 9.34749 s, 54.7 MB/s
511229952 bytes (511 MB) copied, 9.2421 s, 55.3 MB/s
511229952 bytes (511 MB) copied, 9.9364 s, 51.5 MB/s
511229952 bytes (511 MB) copied, 10.0337 s, 51.0 MB/s
511229952 bytes (511 MB) copied, 9.39502 s, 54.4 MB/s
versus the qemu numbers:
511229952 bytes (511 MB) copied, 10.0879 s, 50.7 MB/s
511229952 bytes (511 MB) copied, 4.92686 s, 104 MB/s
511229952 bytes (511 MB) copied, 13.1955 s, 38.7 MB/s
511229952 bytes (511 MB) copied, 10.7322 s, 47.6 MB/s
511229952 bytes (511 MB) copied, 9.46115 s, 54.0 MB/s
511229952 bytes (511 MB) copied, 14.9963 s, 34.1 MB/s
511229952 bytes (511 MB) copied, 11.1701 s, 45.8 MB/s
but indeed there's (much) more variability in the Qemu numbers,
suggesting some cache artifact.
Are all of these measurements done via /dev/shm, to stabilize the
numbers and to remove disk IO delay artifacts?
Thanks,
Ingo
next prev parent reply other threads:[~2011-07-11 10:36 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-09 13:02 [PATCH 0/9] kvm tools, qcow: Improve QCOW performance Pekka Enberg
2011-07-09 13:02 ` [PATCH 1/9] kvm tools, qcow: Rename struct qcow_l2_cache to struct qcow_l2_table Pekka Enberg
2011-07-09 13:02 ` [PATCH 2/9] kvm tools, qcow: Use 'struct qcow_l2_table' instead of untyped array Pekka Enberg
2011-07-09 13:02 ` [PATCH 3/9] kvm tools, qcow: Fix locking issues Pekka Enberg
2011-07-09 13:02 ` [PATCH 4/9] kvm tools, qcow: Introduce qcow_disk_flush() Pekka Enberg
2011-07-09 13:02 ` [PATCH 5/9] kvm tools, qcow: Delayed L1 table writeout Pekka Enberg
2011-07-09 13:02 ` [PATCH 6/9] kvm tools, qcow: Don't fdatasync() L2 " Pekka Enberg
2011-07-09 13:02 ` [PATCH 7/9] kvm tools, qcow: Use big endian order for L2 table entries Pekka Enberg
2011-07-09 13:02 ` [PATCH 8/9] kvm tools, qcow: Delayed L2 table writeout Pekka Enberg
2011-07-09 13:02 ` [PATCH 9/9] kvm tools, qcow: Flush only dirty L2 tables Pekka Enberg
2011-07-10 17:15 ` [PATCH 0/9] kvm tools, qcow: Improve QCOW performance Ingo Molnar
2011-07-10 18:08 ` Pekka Enberg
2011-07-10 18:17 ` Ingo Molnar
2011-07-10 18:38 ` Pekka Enberg
2011-07-11 9:31 ` Kevin Wolf
2011-07-11 9:41 ` Pekka Enberg
2011-07-11 10:29 ` Kevin Wolf
2011-07-11 10:32 ` Pekka Enberg
2011-07-11 10:36 ` Ingo Molnar [this message]
2011-07-11 10:44 ` Pekka Enberg
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