From: "Lukáš Czerner" <lczerner@redhat.com>
To: Prashant Shah <pshah.mumbai@gmail.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: Fwd: block level cow operation
Date: Tue, 9 Apr 2013 11:56:49 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.00.1304091152430.22989@localhost> (raw)
In-Reply-To: <CAD6i1f+NLF6Vj8D84FFWAbDttqbBvcg-kWswf7Hez2o0-cXpMw@mail.gmail.com>
On Tue, 9 Apr 2013, Prashant Shah wrote:
> Date: Tue, 9 Apr 2013 14:35:56 +0530
> From: Prashant Shah <pshah.mumbai@gmail.com>
> To: linux-ext4@vger.kernel.org
> Subject: Fwd: block level cow operation
>
> Hi,
>
> I am trying to implement copy on write operation
Hi,
In ext4 ? Why are you trying to do that ?
> by reading the
> original disk block and writing it to some other location and then
> allowing the write to pass though (block the write operation till the
> read or original block completes) I tried using submit_bio() /
> sb_bread() to read the block and using the completion API to signal
> the end of reading the block but the performance of this is very bad.
> It takes around 12 times more time for any disk writes. Is there any
> better way to improve the performance ?
I am not sure what you're trying to achieve here, but the simplest
answer is yes, there is a way to improve the performance - use
device mapper to do this. thinp target provides you with block level
cow functionality which enables you to do snapshots efficiently for
example.
-Lukas
>
> Not waiting for the completion of the read operation and letting the
> disk write go through gives good performance but under 10% of the
> cases the read happens after the write and ends up the the new data
> and not the original data.
>
> Regards.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
next prev parent reply other threads:[~2013-04-09 9:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAD6i1f+GsVZJwaz1R3NDjP_m8nOCUsmqHTQS3R=M+d+hq8f5vw@mail.gmail.com>
2013-04-09 9:05 ` Fwd: block level cow operation Prashant Shah
2013-04-09 9:56 ` Lukáš Czerner [this message]
2013-04-09 14:46 ` Dmitry Monakhov
2013-04-25 13:00 ` Prashant Shah
2013-05-10 13:14 ` Prashant Shah
2013-04-09 21:02 ` Theodore Ts'o
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=alpine.LFD.2.00.1304091152430.22989@localhost \
--to=lczerner@redhat.com \
--cc=linux-ext4@vger.kernel.org \
--cc=pshah.mumbai@gmail.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).