xfs
[Top] [All Lists]

Re: hole punching performance

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: hole punching performance
From: Florian Weimer <fw@xxxxxxxxxxxxx>
Date: Tue, 15 Jan 2013 22:31:08 +0100
Cc: Ben Myers <bpm@xxxxxxx>, xfs@xxxxxxxxxxx, "Bradley C. Kuszmaul" <kuszmaul@xxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130113225545.GA19173@dastard> (Dave Chinner's message of "Mon, 14 Jan 2013 09:55:45 +1100")
References: <CAKSyJXf66H2U-BF-aYnSr2fF24_6LJw6swOx1RhUc_3Eqayaiw@xxxxxxxxxxxxxx> <87pq195t8q.fsf@xxxxxxxxxxxxxxxxx> <CAKSyJXfQsmemZ3H9A92UezsPCXfn37LXP3tpPMkiwtvR4=eY2g@xxxxxxxxxxxxxx> <20130113194941.GB27055@xxxxxxx> <20130113225545.GA19173@dastard>
* Dave Chinner:

> On Sun, Jan 13, 2013 at 01:49:41PM -0600, Ben Myers wrote:
>> On Sun, Jan 13, 2013 at 11:36:27AM -0500, Bradley C. Kuszmaul wrote:
>> > On Sun, Jan 13, 2013 at 4:26 AM, Florian Weimer <fw@xxxxxxxxxxxxx> wrote:
>> > > I once was a heavy Berkeley DB user and had files with dozens
>> > > of gigabytes containing hundreds of thousands of extents, and
>> > > open() times in the order of minutes were not unusual with a
>> > > cold cache and other concurrent read activities from the same
>> > > RAID device.
>> 
>> Ouch.  I would not have expected open times that bad.
>
> That will only happen if the extent list needs to be read during the
> open() call. That will only occur if O_TRUNC is set. Otherwise, the
> extents are read on the first syscall that needs them to be read in
> (read, write, alloc, punch, truncate, etc) and that's when the
> latency occurs.

Indeed, I think I have misremembered.  The delay occurred when
Berkeley DB tried to read the first page from disk.

<Prev in Thread] Current Thread [Next in Thread>