From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Lieven <pl@kamp.de>
Cc: "Benoît Canet" <benoit.canet@irqsave.net>,
"Kevin Wolf" <kwolf@redhat.com>,
"ronnie sahlberg" <ronniesahlberg@gmail.com>,
qemu-devel <qemu-devel@nongnu.org>,
"Max Reitz" <mreitz@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/4] block: immediately cancel oversized read/write requests
Date: Mon, 08 Sep 2014 18:29:58 +0200 [thread overview]
Message-ID: <540DD986.8010301@redhat.com> (raw)
In-Reply-To: <29A6ECA0-C6CE-4557-80CA-31FD2CA199A2@kamp.de>
Il 08/09/2014 18:18, Peter Lieven ha scritto:
>> > When copying data, gparted will try using very large I/O sizes. Of
>> > course if something breaks it will just use a smaller size, but it would
>> > make performance worse.
>> >
>> > I tried now (with local storage, not virtual---but with such large block
>> > sizes it's disk bound anyway, one request can take 0.1 seconds to
>> > execute) and a 2 MB block size is 20% slower than 16 MB block size on
>> > your usual 3.5" rotational SATA disk.
>> >
> can you share with what command exactly you ran these tests?
>
> i tried myself and found that without multiwrite_merge i was not able to create a request bigger than 0xffff sectors from inside linux.
On a different machine:
$ time dd if=/dev/zero of=test bs=16777216 count=30 oflag=direct
real 0m13.497s
user 0m0.001s
sys 0m0.541s
$ time dd if=/dev/zero of=test2 bs=1048576 count=480 oflag=direct
real 0m15.835s
user 0m0.005s
sys 0m0.770s
The bigger block size is 17% faster; for disk-to-disk copy:
$ time dd if=test of=test3 bs=16777216 count=30 iflag=direct oflag=direct
real 0m26.075s
user 0m0.001s
sys 0m0.678s
$ time dd if=test2 of=test4 bs=1048576 count=480 iflag=direct oflag=direct
real 0m45.210s
user 0m0.005s
sys 0m1.145s
The bigger block size is 73% faster.
Paolo
next prev parent reply other threads:[~2014-09-08 16:30 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-05 16:51 [Qemu-devel] [PATCH 0/4] introduce max_transfer_length Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 1/4] BlockLimits: " Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 2/4] block: immediately cancel oversized read/write requests Peter Lieven
2014-09-08 13:44 ` Benoît Canet
2014-09-08 13:49 ` Paolo Bonzini
2014-09-08 13:56 ` Peter Lieven
2014-09-08 13:58 ` Paolo Bonzini
2014-09-08 14:35 ` Peter Lieven
2014-09-08 14:42 ` Paolo Bonzini
2014-09-08 14:54 ` Peter Lieven
2014-09-23 8:47 ` Kevin Wolf
2014-09-23 8:55 ` Peter Lieven
2014-09-23 9:09 ` Kevin Wolf
2014-09-08 15:13 ` ronnie sahlberg
2014-09-08 15:15 ` Paolo Bonzini
2014-09-08 15:18 ` Peter Lieven
2014-09-08 15:27 ` Paolo Bonzini
2014-09-08 16:18 ` Peter Lieven
2014-09-08 16:29 ` Paolo Bonzini [this message]
2014-09-12 11:43 ` Peter Lieven
2014-09-18 14:12 ` Paolo Bonzini
2014-09-18 14:16 ` Peter Lieven
2014-09-18 14:17 ` Paolo Bonzini
2014-09-18 22:57 ` Peter Lieven
2014-09-08 15:16 ` Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 3/4] block/iscsi: set max_transfer_length Peter Lieven
2014-09-05 16:51 ` [Qemu-devel] [PATCH 4/4] block: avoid creating oversized writes in multiwrite_merge Peter Lieven
2014-09-18 14:13 ` Paolo Bonzini
2014-09-18 22:56 ` Peter Lieven
2014-09-19 13:33 ` Paolo Bonzini
2014-09-22 9:43 ` Peter Lieven
2014-09-22 19:06 ` Paolo Bonzini
2014-09-23 6:15 ` Peter Lieven
2014-09-23 8:59 ` Kevin Wolf
2014-09-23 9:04 ` Peter Lieven
2014-09-23 9:32 ` Peter Lieven
2014-09-23 9:47 ` Kevin Wolf
2014-09-23 9:52 ` Peter Lieven
2014-09-23 10:05 ` Kevin Wolf
2014-09-30 7:26 ` Peter Lieven
2014-09-30 8:03 ` Kevin Wolf
2014-09-05 17:05 ` [Qemu-devel] [PATCH 0/4] introduce max_transfer_length ronnie sahlberg
2014-09-05 19:52 ` Peter Lieven
2014-09-05 21:22 ` ronnie sahlberg
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=540DD986.8010301@redhat.com \
--to=pbonzini@redhat.com \
--cc=benoit.canet@irqsave.net \
--cc=kwolf@redhat.com \
--cc=mreitz@redhat.com \
--cc=pl@kamp.de \
--cc=qemu-devel@nongnu.org \
--cc=ronniesahlberg@gmail.com \
--cc=stefanha@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.