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

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Message-ID: <20200618173527.GR8681@bombadil.infradead.org>
Date:   Thu, 18 Jun 2020 10:35:27 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     "Paul E. McKenney" <paulmck@...nel.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 07:30:49PM +0200, Uladzislau Rezki wrote:
> > I'd suggest:
> > 
> >  			rcu_lock_acquire(&rcu_callback_map);
> > 			trace_rcu_invoke_kfree_bulk_callback(rcu_state.name,
> > 				bkvhead[i]->nr_records, bkvhead[i]->records);
> >  			if (i == 0) {
> >  				kfree_bulk(bkvhead[i]->nr_records,
> >  					bkvhead[i]->records);
> >  			} else {
> >  				for (j = 0; j < bkvhead[i]->nr_records; j++) {
> >  					vfree(bkvhead[i]->records[j]);
> >  				}
> >  			}
> >  			rcu_lock_release(&rcu_callback_map);
> >
> There are two different trace functions, one for "bulk" tracing
> messages, and another one is per one call of kfree(), though we use 
> to indicate vfree() call.
> 
> Probably we can rename it to: trace_rcu_invoke_kvfree_callback();
> 
> What do you think?

Works for me!

> > But I'd also suggest a vfree_bulk be added.  There are a few things
> > which would be better done in bulk as part of the vfree process
> > (we batch them up already, but i'm sure we could do better).
> 
> I was thinking to implement of vfree_bulk() API, but i guess it can
> be done as future work.
> 
> Does that sound good?

Yes, definitely a future piece of work.