From: Mel Gorman <mgorman@techsingularity.net>
To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: 'Jesper Dangaard Brouer' <brouer@redhat.com>,
'Linux Kernel' <linux-kernel@vger.kernel.org>,
'Linux-MM' <linux-mm@kvack.org>
Subject: Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
Date: Mon, 9 Jan 2017 09:48:01 +0000 [thread overview]
Message-ID: <20170109094801.bkif6komfepc3rcx@techsingularity.net> (raw)
In-Reply-To: <019901d26a26$7def6c30$79ce4490$@alibaba-inc.com>
On Mon, Jan 09, 2017 at 11:14:29AM +0800, Hillf Danton wrote:
> > Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
> >
> > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> > >
> > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > struct list_head *list;
> > > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > > struct page *page;
> > > > - unsigned long flags;
> > > >
> > > > - local_irq_save(flags);
> > > > + preempt_disable();
> > > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > > list = &pcp->lists[migratetype];
> > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > > }
> > > > - local_irq_restore(flags);
> > > > + preempt_enable();
> > > > return page;
> > > > }
> > > >
> > > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > > Is that needed when we try to allocate a page?
> > >
> >
> > Not necessarily but what are you proposing as an alternative?
>
> preempt_enable_no_resched() looks at first glance a choice for us to
> avoid flipping interrupts.
>
Ok, I wasn't sure if you were proposing something more drastic. I can
make it this although I have no reason to believe it will really matter.
The path should be short enough that it's unlikely a scheduler event
would ever occur at that point. Still, no harm in doing what you
suggest.
Thanks.
--
Mel Gorman
SUSE Labs
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WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@techsingularity.net>
To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: "'Jesper Dangaard Brouer'" <brouer@redhat.com>,
"'Linux Kernel'" <linux-kernel@vger.kernel.org>,
"'Linux-MM'" <linux-mm@kvack.org>
Subject: Re: [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests
Date: Mon, 9 Jan 2017 09:48:01 +0000 [thread overview]
Message-ID: <20170109094801.bkif6komfepc3rcx@techsingularity.net> (raw)
In-Reply-To: <019901d26a26$7def6c30$79ce4490$@alibaba-inc.com>
On Mon, Jan 09, 2017 at 11:14:29AM +0800, Hillf Danton wrote:
> > Sent: Friday, January 06, 2017 6:16 PM Mel Gorman wrote:
> >
> > On Fri, Jan 06, 2017 at 11:26:46AM +0800, Hillf Danton wrote:
> > >
> > > On Wednesday, January 04, 2017 7:11 PM Mel Gorman wrote:
> > > > @@ -2647,9 +2644,8 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > struct list_head *list;
> > > > bool cold = ((gfp_flags & __GFP_COLD) != 0);
> > > > struct page *page;
> > > > - unsigned long flags;
> > > >
> > > > - local_irq_save(flags);
> > > > + preempt_disable();
> > > > pcp = &this_cpu_ptr(zone->pageset)->pcp;
> > > > list = &pcp->lists[migratetype];
> > > > page = __rmqueue_pcplist(zone, order, gfp_flags, migratetype,
> > > > @@ -2658,7 +2654,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
> > > > __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> > > > zone_statistics(preferred_zone, zone, gfp_flags);
> > > > }
> > > > - local_irq_restore(flags);
> > > > + preempt_enable();
> > > > return page;
> > > > }
> > > >
> > > With PREEMPT configured, preempt_enable() adds entry point to schedule().
> > > Is that needed when we try to allocate a page?
> > >
> >
> > Not necessarily but what are you proposing as an alternative?
>
> preempt_enable_no_resched() looks at first glance a choice for us to
> avoid flipping interrupts.
>
Ok, I wasn't sure if you were proposing something more drastic. I can
make it this although I have no reason to believe it will really matter.
The path should be short enough that it's unlikely a scheduler event
would ever occur at that point. Still, no harm in doing what you
suggest.
Thanks.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2017-01-09 9:48 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-04 11:10 [RFC PATCH 0/4] Fast noirq bulk page allocator Mel Gorman
2017-01-04 11:10 ` Mel Gorman
2017-01-04 11:10 ` [PATCH 1/4] mm, page_alloc: Split buffered_rmqueue Mel Gorman
2017-01-04 11:10 ` Mel Gorman
2017-01-04 11:10 ` [PATCH 2/4] mm, page_alloc: Split alloc_pages_nodemask Mel Gorman
2017-01-04 11:10 ` Mel Gorman
2017-01-04 11:10 ` [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests Mel Gorman
2017-01-04 11:10 ` Mel Gorman
2017-01-04 14:20 ` Jesper Dangaard Brouer
2017-01-04 14:20 ` Jesper Dangaard Brouer
2017-01-06 3:26 ` Hillf Danton
2017-01-06 3:26 ` Hillf Danton
2017-01-06 10:15 ` Mel Gorman
2017-01-06 10:15 ` Mel Gorman
2017-01-09 3:14 ` Hillf Danton
2017-01-09 3:14 ` Hillf Danton
2017-01-09 9:48 ` Mel Gorman [this message]
2017-01-09 9:48 ` Mel Gorman
2017-01-09 9:55 ` Hillf Danton
2017-01-09 9:55 ` Hillf Danton
2017-01-04 11:10 ` [PATCH 4/4] mm, page_alloc: Add a bulk page allocator Mel Gorman
2017-01-04 11:10 ` Mel Gorman
2017-01-04 13:48 ` Jesper Dangaard Brouer
2017-01-04 13:48 ` Jesper Dangaard Brouer
2017-01-04 14:03 ` Mel Gorman
2017-01-04 14:03 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2017-01-09 16:35 [RFC PATCH 0/4] Fast noirq bulk page allocator v2r7 Mel Gorman
2017-01-09 16:35 ` [PATCH 3/4] mm, page_allocator: Only use per-cpu allocator for irq-safe requests Mel Gorman
2017-01-09 16:35 ` Mel Gorman
2017-01-11 12:44 ` Jesper Dangaard Brouer
2017-01-11 12:44 ` Jesper Dangaard Brouer
2017-01-11 13:27 ` Jesper Dangaard Brouer
2017-01-11 13:27 ` Jesper Dangaard Brouer
2017-01-12 10:47 ` Mel Gorman
2017-01-12 10:47 ` Mel Gorman
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