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

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Date:   Thu, 18 Jun 2020 22:03:33 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        "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 10:35:27AM -0700, Matthew Wilcox wrote:
> 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!
> 
OK. I will send out the patch that will rename that trace function
that makes clear that the pointer that is freed can belong to SLAB
or vmalloc.

> > > 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.
>
You have already been doing it.

Thank you, Matthew :)

--
Vlad Rezki