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Re: [PATCH] xfstests: add execution of a custom command to fsstress (-x

To: Jan Schmidt <list.xfs@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfstests: add execution of a custom command to fsstress (-x and -X options)
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 22 Mar 2013 08:12:18 +1100
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <514B72B9.1010005@xxxxxxxxxxxxx>
References: <1363863585-25598-1-git-send-email-list.xfs@xxxxxxxxxxxxx> <20130321195054.GO17758@dastard> <514B72B9.1010005@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Mar 21, 2013 at 09:51:05PM +0100, Jan Schmidt wrote:
> 
> 
> On 21.03.2013 20:50, Dave Chinner wrote:
> > On Thu, Mar 21, 2013 at 11:59:45AM +0100, Jan Schmidt wrote:
> >> From: Jan Schmidt <list.btrfs@xxxxxxxxxxxxx>
> >>
> >> This patch adds execution of a custom command in the middle of all fsstress
> >> operations. Its intended use is the creation of snapshots in the middle of 
> >> a
> >> test run.
> > 
> > Why do you need fsstress to do this? Why can't you just run fsstress
> > in the background and run a loop creating periodic snapshots in the
> > control script?
> 
> Because I want reproducible results. Same random seed should result in
> the very same snapshots being created.

Why can't you run fsstress for N operations, run a snapshot,
then run it again for M operations? That will give you exactly the
same results, wouldn't it?

> > Also, did you intend that every process creates a snapshot? i.e. it
> > looks lik eif you run a 1000 processes, they'll all run a snapshot
> > operation at X operations? i.e. this will generate nproc * X
> > snapshots in a single run. This doesn't seem very wise to me....
> 
> Agreed, I haven't thought of running more than one process. For the sake
> of reproducibility, I wouldn't want multiple processes for my test case
> either.
> 
> I'm not sure if there are other applications than snapshot creation for
> such a feature, so I cannot argue whether to have each process execute
> such a command or not.

If such a feature is necessary, I'd suggest that implementing the
snapshot ioctl as just another operation directly into fsstress is
probably a better way to implement this functionality. That way you
can control the frequency via the command line in exactly the same
way as every other operation....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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