linux-kernel - Re: [PATCH v2 09/16] rcu/tree: Maintain separate array for vmalloc ptrs

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Message-ID: <20200618190359.GU2723@paulmck-ThinkPad-P72>
Date:   Thu, 18 Jun 2020 12:03:59 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Joel Fernandes <joel@...lfernandes.org>,
        RCU <rcu@...r.kernel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH v2 09/16] rcu/tree: Maintain separate array for vmalloc
 ptrs

On Thu, Jun 18, 2020 at 08:34:48PM +0200, Uladzislau Rezki wrote:
> > > > 
> > > > I suspect that he would like to keep the tracing.
> > > > 
> > > > It might be worth trying the branches, given that they would be constant
> > > > and indexed by "i".  The compiler might well remove the indirection.
> > > > 
> > > > The compiler guys brag about doing so, which of course might or might
> > > > not have any correlation to a given compiler actually doing so.  :-/
> > > > 
> > > > Having a vfree_bulk() might well be useful, but I would feel more
> > > > confidence in that if there were other callers of kfree_bulk().
> > > >
> > > Hmm... I think replacing that with vfree_bulk() is a good idea though.
> > 
> > In other words, get rid of kfree_bulk() in favor of vfree_bulk()?
> > 
> kfree_bulk() does not understand vmalloc memory. vfree_bulk() should
> be implemented to release vmalloc's pointers. On i high level it will
> be used the same way as kfree_bulk() but for vmalloc ptrs. only.

Ah, I thought that you guys were proposing something that did bulk
free of both kmalloc and vmalloc memory.

							Thanx, Paul

> > > > But again, either way, future work as far as this series is concerned.
> > > > 
> > > What do you mean: is concerned?
> > 
> > Apologies for the strange English.  How about this?
> > 
> > "This series is OK as is.  Any comments above did not prevent me from
> > taking these patches, but instead discuss possible future work."
> > 
> That is perfectly clear to me :)
> 
> > > We are planning to implement kfree_rcu() to be integrated directly into
> > > SLAB: SLAB, SLUB, SLOB. So, there are plenty of future work :)
> >
> > And I am glad that this is still the goal.  ;-)
> >
> :)
> 
> --
> Vlad Rezki