From: Michal Hocko <mhocko@kernel.org>
To: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
vbabka@suse.cz, rientjes@google.com, mgorman@techsingularity.net,
liangchen.linux@gmail.com, nzimmer@sgi.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/mempolicy.c: forbid static or relative flags for local NUMA mode
Date: Mon, 19 Sep 2016 13:52:05 +0200 [thread overview]
Message-ID: <20160919115204.GL10785@dhcp22.suse.cz> (raw)
In-Reply-To: <20160918112943.1645-1-kwapulinski.piotr@gmail.com>
On Sun 18-09-16 13:29:43, Piotr Kwapulinski wrote:
> The MPOL_F_STATIC_NODES and MPOL_F_RELATIVE_NODES flags are irrelevant
> when setting them for MPOL_LOCAL NUMA memory policy via set_mempolicy.
> Return the "invalid argument" from set_mempolicy whenever
> any of these flags is passed along with MPOL_LOCAL.
man 2 set_mempolicy doesn't list this as invalid option. Maybe this is a
documentation bug but is it possible that somebody will see this as an
unexpected error?
> It is consistent with MPOL_PREFERRED passed with empty nodemask.
> It also slightly shortens the execution time in paths where these flags
> are used e.g. when trying to rebind the NUMA nodes for changes in
> cgroups cpuset mems (mpol_rebind_preferred()) or when just printing
> the mempolicy structure (/proc/PID/numa_maps).
I am not sure I understand this argument. What does this patch actually
fix? If this is about the execution time then why not just bail out
early when MPOL_LOCAL && (MPOL_F_STATIC_NODES || MPOL_F_RELATIVE_NODES)
> Isolated tests done.
>
> Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
> ---
> mm/mempolicy.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 2da72a5..27b07d1 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -276,7 +276,9 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags,
> return ERR_PTR(-EINVAL);
> }
> } else if (mode == MPOL_LOCAL) {
> - if (!nodes_empty(*nodes))
> + if (!nodes_empty(*nodes) ||
> + (flags & MPOL_F_STATIC_NODES) ||
> + (flags & MPOL_F_RELATIVE_NODES))
> return ERR_PTR(-EINVAL);
> mode = MPOL_PREFERRED;
> } else if (nodes_empty(*nodes))
> --
> 2.9.2
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-09-19 11:52 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-18 11:29 Piotr Kwapulinski
2016-09-19 11:52 ` Michal Hocko [this message]
2016-09-20 15:47 ` Piotr Kwapulinski
2016-09-20 0:57 ` David Rientjes
2016-09-20 15:56 ` Piotr Kwapulinski
2016-09-20 20:05 ` David Rientjes
2016-09-27 13:19 ` [PATCH 0/1] man/set_mempolicy.2,mbind.2: add MPOL_LOCAL NUMA memory policy documentation Piotr Kwapulinski
2016-10-04 8:36 ` Christoph Lameter
2016-10-09 18:56 ` [PATCH v2 " Piotr Kwapulinski
2016-10-10 13:55 ` Christoph Lameter
2016-10-10 16:23 ` [PATCH v3 " Piotr Kwapulinski
2016-10-12 7:55 ` Michael Kerrisk (man-pages)
2016-10-12 14:08 ` Christoph Lameter
2016-10-12 14:35 ` Michael Kerrisk (man-pages)
2016-10-12 15:53 ` Piotr Kwapulinski
2016-10-12 19:55 ` Christoph Lameter
2016-10-13 6:48 ` Michael Kerrisk (man-pages)
2016-09-27 13:22 ` [PATCH 1/1] mm/mempolicy.c: " Piotr Kwapulinski
2016-09-27 13:25 ` [PATCH v2 0/1] mm/mempolicy.c: forbid static or relative flags for local NUMA mode Piotr Kwapulinski
2016-10-27 16:30 ` [PATCH v3 " Piotr Kwapulinski
2016-11-01 0:21 ` David Rientjes
2016-09-27 13:27 ` [PATCH 1/1] man/set_mempolicy.2,mbind.2: " Piotr Kwapulinski
2016-09-20 15:12 ` [PATCH] mm/mempolicy.c: " Vlastimil Babka
2016-09-20 16:23 ` Piotr Kwapulinski
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