From: Andrea Arcangeli <aarcange@redhat.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <pzijlstr@redhat.com>, Ingo Molnar <mingo@elte.hu>,
Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Hillf Danton <dhillf@gmail.com>,
Andrew Jones <drjones@redhat.com>, Dan Smith <danms@us.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Paul Turner <pjt@google.com>, Christoph Lameter <cl@linux.com>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Mike Galbraith <efault@gmx.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 06/33] autonuma: teach gup_fast about pmd_numa
Date: Thu, 11 Oct 2012 19:05:33 +0200 [thread overview]
Message-ID: <20121011170533.GP1818@redhat.com> (raw)
In-Reply-To: <20121011122255.GS3317@csn.ul.ie>
On Thu, Oct 11, 2012 at 01:22:55PM +0100, Mel Gorman wrote:
> On Thu, Oct 04, 2012 at 01:50:48AM +0200, Andrea Arcangeli wrote:
> > In the special "pmd" mode of knuma_scand
> > (/sys/kernel/mm/autonuma/knuma_scand/pmd == 1), the pmd may be of numa
> > type (_PAGE_PRESENT not set), however the pte might be
> > present. Therefore, gup_pmd_range() must return 0 in this case to
> > avoid losing a NUMA hinting page fault during gup_fast.
> >
>
> So if gup_fast fails, presumably we fall back to taking the mmap_sem and
> calling get_user_pages(). This is a heavier operation and I wonder if the
> cost is justified. i.e. Is the performance loss from using get_user_pages()
> offset by improved NUMA placement? I ask because we always incur the cost of
> taking mmap_sem but only sometimes get it back from improved NUMA placement.
> How bad would it be if gup_fast lost some of the NUMA hinting information?
Good question indeed. Now, I agree it wouldn't be bad to skip NUMA
hinting page faults in gup_fast for no-virt usage like
O_DIRECT/ptrace, but the only problem is that we'd lose AutoNUMA on
the memory touched by the KVM vcpus.
I've been also asked if the vhost-net kernel thread (KVM in kernel
virtio backend) will be controlled by autonuma in between
use_mm/unuse_mm and answer is yes, but to do that, it also needs
this. (see also the flush to task_autonuma_nid and mm/task statistics in
unuse_mm to reset it back to regular kernel thread status,
uncontrolled by autonuma)
$ git grep get_user_pages
tcm_vhost.c: ret = get_user_pages_fast((unsigned long)ptr, 1, write, &page);
vhost.c: r = get_user_pages_fast(log, 1, 1, &page);
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next prev parent reply other threads:[~2012-10-11 17:06 UTC|newest]
Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-03 23:50 [PATCH 00/33] AutoNUMA27 Andrea Arcangeli
2012-10-03 23:50 ` [PATCH 01/33] autonuma: add Documentation/vm/autonuma.txt Andrea Arcangeli
2012-10-11 10:50 ` Mel Gorman
2012-10-11 16:07 ` Andrea Arcangeli
2012-10-11 19:37 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 02/33] autonuma: make set_pmd_at always available Andrea Arcangeli
2012-10-11 10:54 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 03/33] autonuma: export is_vma_temporary_stack() even if CONFIG_TRANSPARENT_HUGEPAGE=n Andrea Arcangeli
2012-10-11 10:54 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 04/33] autonuma: define _PAGE_NUMA Andrea Arcangeli
2012-10-11 11:01 ` Mel Gorman
2012-10-11 16:43 ` Andrea Arcangeli
2012-10-11 19:48 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 05/33] autonuma: pte_numa() and pmd_numa() Andrea Arcangeli
2012-10-11 11:15 ` Mel Gorman
2012-10-11 16:58 ` Andrea Arcangeli
2012-10-11 19:54 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 06/33] autonuma: teach gup_fast about pmd_numa Andrea Arcangeli
2012-10-11 12:22 ` Mel Gorman
2012-10-11 17:05 ` Andrea Arcangeli [this message]
2012-10-11 20:01 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 07/33] autonuma: mm_autonuma and task_autonuma data structures Andrea Arcangeli
2012-10-11 12:28 ` Mel Gorman
2012-10-11 15:24 ` Rik van Riel
2012-10-11 15:57 ` Mel Gorman
2012-10-12 0:23 ` Christoph Lameter
2012-10-12 0:52 ` Andrea Arcangeli
2012-10-11 17:15 ` Andrea Arcangeli
2012-10-11 20:06 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 08/33] autonuma: define the autonuma flags Andrea Arcangeli
2012-10-11 13:46 ` Mel Gorman
2012-10-11 17:34 ` Andrea Arcangeli
2012-10-11 20:17 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 09/33] autonuma: core autonuma.h header Andrea Arcangeli
2012-10-03 23:50 ` [PATCH 10/33] autonuma: CPU follows memory algorithm Andrea Arcangeli
2012-10-11 14:58 ` Mel Gorman
2012-10-12 0:25 ` Andrea Arcangeli
2012-10-12 8:29 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 11/33] autonuma: add the autonuma_last_nid in the page structure Andrea Arcangeli
2012-10-03 23:50 ` [PATCH 12/33] autonuma: Migrate On Fault per NUMA node data Andrea Arcangeli
2012-10-11 15:43 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 13/33] autonuma: autonuma_enter/exit Andrea Arcangeli
2012-10-11 13:50 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 14/33] autonuma: call autonuma_setup_new_exec() Andrea Arcangeli
2012-10-11 15:47 ` Mel Gorman
2012-10-03 23:50 ` [PATCH 15/33] autonuma: alloc/free/init task_autonuma Andrea Arcangeli
2012-10-11 15:53 ` Mel Gorman
2012-10-11 17:34 ` Rik van Riel
[not found] ` <20121011175953.GT1818@redhat.com>
2012-10-12 14:03 ` Rik van Riel
2012-10-03 23:50 ` [PATCH 16/33] autonuma: alloc/free/init mm_autonuma Andrea Arcangeli
2012-10-03 23:50 ` [PATCH 17/33] autonuma: prevent select_task_rq_fair to return -1 Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 18/33] autonuma: teach CFS about autonuma affinity Andrea Arcangeli
2012-10-05 6:41 ` Mike Galbraith
2012-10-05 11:54 ` Andrea Arcangeli
2012-10-06 2:39 ` Mike Galbraith
2012-10-06 12:34 ` Andrea Arcangeli
2012-10-07 6:07 ` Mike Galbraith
2012-10-08 7:03 ` Mike Galbraith
2012-10-03 23:51 ` [PATCH 19/33] autonuma: memory follows CPU algorithm and task/mm_autonuma stats collection Andrea Arcangeli
2012-10-10 22:01 ` Rik van Riel
2012-10-10 22:36 ` Andrea Arcangeli
2012-10-11 18:28 ` Mel Gorman
2012-10-13 18:06 ` Srikar Dronamraju
2012-10-15 8:24 ` Srikar Dronamraju
2012-10-15 9:20 ` Mel Gorman
2012-10-15 10:00 ` Srikar Dronamraju
2012-10-03 23:51 ` [PATCH 20/33] autonuma: default mempolicy follow AutoNUMA Andrea Arcangeli
2012-10-04 20:03 ` KOSAKI Motohiro
2012-10-11 18:32 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 21/33] autonuma: call autonuma_split_huge_page() Andrea Arcangeli
2012-10-11 18:33 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 22/33] autonuma: make khugepaged pte_numa aware Andrea Arcangeli
2012-10-11 18:36 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 23/33] autonuma: retain page last_nid information in khugepaged Andrea Arcangeli
2012-10-11 18:44 ` Mel Gorman
2012-10-12 11:37 ` Rik van Riel
2012-10-12 12:35 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 24/33] autonuma: split_huge_page: transfer the NUMA type from the pmd to the pte Andrea Arcangeli
2012-10-11 18:45 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 25/33] autonuma: numa hinting page faults entry points Andrea Arcangeli
2012-10-11 18:47 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 26/33] autonuma: reset autonuma page data when pages are freed Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 27/33] autonuma: link mm/autonuma.o and kernel/sched/numa.o Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 28/33] autonuma: add CONFIG_AUTONUMA and CONFIG_AUTONUMA_DEFAULT_ENABLED Andrea Arcangeli
2012-10-11 18:50 ` Mel Gorman
2012-10-03 23:51 ` [PATCH 29/33] autonuma: page_autonuma Andrea Arcangeli
2012-10-04 14:16 ` Christoph Lameter
2012-10-04 20:09 ` KOSAKI Motohiro
2012-10-05 11:31 ` Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 30/33] autonuma: bugcheck page_autonuma fields on newly allocated pages Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 31/33] autonuma: boost khugepaged scanning rate Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 32/33] autonuma: add migrate_allow_first_fault knob in sysfs Andrea Arcangeli
2012-10-03 23:51 ` [PATCH 33/33] autonuma: add mm_autonuma working set estimation Andrea Arcangeli
2012-10-04 18:39 ` [PATCH 00/33] AutoNUMA27 Andrew Morton
2012-10-04 20:49 ` Rik van Riel
2012-10-05 23:08 ` Rik van Riel
2012-10-05 23:14 ` Andi Kleen
2012-10-05 23:57 ` Tim Chen
2012-10-06 0:11 ` Andi Kleen
2012-10-08 13:44 ` Don Morris
2012-10-08 20:34 ` Rik van Riel
2012-10-11 10:19 ` Mel Gorman
2012-10-11 14:56 ` Andrea Arcangeli
2012-10-11 15:35 ` Mel Gorman
2012-10-12 0:41 ` Andrea Arcangeli
2012-10-12 14:54 ` Mel Gorman
2012-10-11 21:34 ` Mel Gorman
2012-10-12 1:45 ` Andrea Arcangeli
2012-10-12 8:46 ` Mel Gorman
2012-10-13 18:40 ` Srikar Dronamraju
2012-10-14 4:57 ` Andrea Arcangeli
2012-10-15 8:16 ` Srikar Dronamraju
2012-10-23 16:32 ` Srikar Dronamraju
2012-10-16 13:48 ` Mel Gorman
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