linux-kernel - Re: [PATCH v4] staging: lustre: mdc: manage number of modify RPCs in flight

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Message-ID: <20161114172047.GA4989@kroah.com>
Date:   Mon, 14 Nov 2016 18:20:47 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     James Simmons <jsimmons@...radead.org>
Cc:     devel@...verdev.osuosl.org,
        Andreas Dilger <andreas.dilger@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Gregoire Pichon <gregoire.pichon@...l.net>,
        Oleg Drokin <oleg.drokin@...el.com>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH v4] staging: lustre: mdc: manage number of modify RPCs in
 flight

On Mon, Nov 14, 2016 at 04:59:48PM +0000, James Simmons wrote:
> 
> > On Thu, Nov 10, 2016 at 10:51:13AM -0500, James Simmons wrote:
> > > From: Gregoire Pichon <gregoire.pichon@...l.net>
> > > 
> > > This patch is the main client part of a new feature that supports
> > > multiple modify metadata RPCs in parallel. Its goal is to improve
> > > metadata operations performance of a single client, while maintening
> > > the consistency of MDT reply reconstruction and MDT recovery
> > > mechanisms.
> > > 
> > > It allows to manage the number of modify RPCs in flight within
> > > the client obd structure and to assign a virtual index (the tag) to
> > > each modify RPC to help server side cleaning of reply data.
> > > 
> > > The mdc component uses this feature to send multiple modify RPCs
> > > in parallel.
> > 
> > Is this a new feature?  Why should we take this now and not just wait
> > until the code is out of staging?
> 
> Yes on the server side. So the problem on our meta data servers couldn't
> handle writing mulitiple bits of data to the back end disk at ths same
> time.
> 
> One client side the issue was the metadata operations were being 
> serialized by a mutex in the MDC layer. That is what this patch fixed.
> So for the client it would be a performance improvement patch. 

So, it's a "performance" patch, which isn't functionality, so why should
we merge this to staging now?  Why aren't people working on the known
coding issues to get this out of staging instead of working on
performance stuff?

thanks,

greg k-h