linux-kernel - Re: [PATCH 0/3 v3] dcache: make it more scalable on large system

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Message-ID: <20130529204323.GC3243@fieldses.org>
Date:	Wed, 29 May 2013 16:43:23 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Waiman Long <waiman.long@...com>,
	Dave Chinner <david@...morbit.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...hat.com>,
	Miklos Szeredi <mszeredi@...e.cz>, Ian Kent <raven@...maw.net>,
	Sage Weil <sage@...tank.com>, Steve French <sfrench@...ba.org>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Eric Paris <eparis@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, autofs@...r.kernel.org,
	ceph-devel@...r.kernel.org, linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH 0/3 v3] dcache: make it more scalable on large system

On Wed, May 29, 2013 at 10:37:00PM +0200, Andi Kleen wrote:
> > As Dave said before, is the last path component sufficient?  Or how
> > about an inode number?
> 
> Neither works, the profiler needs to find the file and read it.
> 
> inode searching would be incredible expensive,

How fast does it need to be?  Actually analyzing the profile is
something you only do once after everything's over, right?

> unless the file system provided a "open-by-inode" primitive

Well, I suppose there is open_by_handle_at.

--b.

> In normal operation you only have that event when starting up the
> program and when each shared library gets mapped in.
> 
> -Andi
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