From mboxrd@z Thu Jan 1 00:00:00 1970 From: matthias.bgg@googlemail.com (Matthias Brugger) Date: Wed, 08 Feb 2012 11:59:26 +0100 Subject: blktrace vs ftrace In-Reply-To: References: <4F2A6357.3060805@gmail.com> <4F2ADEC9.1090200@gmail.com> Message-ID: <4F32558E.3090804@gmail.com> To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org Hi, On 02/03/2012 06:59 AM, Mulyadi Santosa wrote: > > I could only offer this explanation: > blktrace traces events in block level. In this level, I/O is likely > serialized....unless you have more than one physical disks. > > in ftrace, you see events right before it hits block level operation. > Somewhere between VFS, filesystem operation and I/O scheduling which > deals with queue reordering. In this case, parallel operation is > likely to happen because more than processes could submit read or > write. If I understand the patch which introduces the blk tracer to ftrace (http://lwn.net/Articles/315508/) just uses the blktrace interface. So I wonder why using this influences the I/O behaviour. Best regards, Matthias