From: Uladzislau Rezki <urezki@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Uladzislau Rezki <urezki@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Daniel Wagner <dwagner@suse.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Hillf Danton <hdanton@sina.com>,
Matthew Wilcox <willy@infradead.org>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: Re: [PATCH 1/1] mm/vmalloc: remove preempt_disable/enable when do preloading
Date: Tue, 15 Oct 2019 11:54:47 +0200 [thread overview]
Message-ID: <20191015095447.GA31683@pc636> (raw)
In-Reply-To: <20191014163022.GL317@dhcp22.suse.cz>
> > > > > > : * The preload is done in non-atomic context, thus it allows us
> > > > > > : * to use more permissive allocation masks to be more stable under
> > > > > > : * low memory condition and high memory pressure.
> > > > > > : *
> > > > > > : * Even if it fails we do not really care about that. Just proceed
> > > > > > : * as it is. "overflow" path will refill the cache we allocate from.
> > > > > > : */
> > > > > > : if (!this_cpu_read(ne_fit_preload_node)) {
> > > > > >
> > > > > > Readability nit: local `pva' should be defined here, rather than having
> > > > > > function-wide scope.
> > > > > >
> > > > > > : pva = kmem_cache_alloc_node(vmap_area_cachep, GFP_KERNEL, node);
> > > > > >
> > > > > > Why doesn't this honour gfp_mask? If it's not a bug, please add
> > > > > > comment explaining this.
> > > > > >
> > > > But there is a comment, if understand you correctly:
> > > >
> > > > <snip>
> > > > * Even if it fails we do not really care about that. Just proceed
> > > > * as it is. "overflow" path will refill the cache we allocate from.
> > > > <snip>
> > >
> > > My point is that the alloc_vmap_area() caller passed us a gfp_t but
> > > this code ignores it, as does adjust_va_to_fit_type(). These *look*
> > > like potential bugs. If not, they should be commented so they don't
> > > look like bugs any more ;)
> > >
> > I got it, there was misunderstanding from my side :) I agree.
> >
> > In the first case i should have used and respect the passed "gfp_mask",
> > like below:
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index f48cd0711478..880b6e8cdeae 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -1113,7 +1113,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> > * Just proceed as it is. If needed "overflow" path
> > * will refill the cache we allocate from.
> > */
> > - pva = kmem_cache_alloc_node(vmap_area_cachep, GFP_KERNEL, node);
> > + pva = kmem_cache_alloc_node(vmap_area_cachep,
> > + gfp_mask & GFP_RECLAIM_MASK, node);
> >
> > spin_lock(&vmap_area_lock);
> >
> > It should be sent as a separate patch, i think.
>
> Yes. I do not think this would make any real difference because that
> battle is lost long ago. vmalloc is simply not gfp mask friendly. There
> are places like page table allocation which are hardcoded GFP_KERNEL so
> GFP_NOWAIT semantic is not going to work, really. The above makes sense
> from a pure aesthetic POV, though, I would say.
I agree. Then i will create a patch.
Thank you!
--
Vlad Rezki
prev parent reply other threads:[~2019-10-15 9:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 16:49 [PATCH 1/1] mm/vmalloc: remove preempt_disable/enable when do preloading Uladzislau Rezki (Sony)
2019-10-09 18:21 ` Steven Rostedt
2019-10-09 22:19 ` Andrew Morton
2019-10-10 2:17 ` Steven Rostedt
2019-10-10 15:17 ` Uladzislau Rezki
2019-10-11 23:55 ` Andrew Morton
2019-10-14 14:27 ` Uladzislau Rezki
2019-10-14 16:30 ` Michal Hocko
2019-10-15 9:54 ` Uladzislau Rezki [this message]
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