From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
Subject: Re: Does blkback bypass Dom0's memory buffer?
Date: Wed, 5 Feb 2014 09:46:58 +0100
Message-ID: <52F1FA82.6080101@citrix.com>
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On 04/02/14 22:15, xu cong wrote:
> Does blkback thread bypass Dom0's memory buffer? If I write in DomU
> without O_Direct, the data will be buffered in DomU's memory cache then
> be flushed to disk. Will them be buffered in Dom0's memory again? How
> about the netback? Thanks.

Blkback will not do any kind of buffering itself, the request is read
from the shared ring and passed to the underlying device using
submit_bio. If you want to make sure your data has hit the disk you
should issue a flush operation (see "feature-flush-cache" in blkif.h)

Roger.