From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>,
Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH V4] mm: Add sysfs interface to dump each node's zonelist information
Date: Mon, 12 Sep 2016 10:54:17 +0530 [thread overview]
Message-ID: <57D63C01.9090309@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160909133648.GL4844@dhcp22.suse.cz>
On 09/09/2016 07:06 PM, Michal Hocko wrote:
> On Thu 08-09-16 08:16:58, Anshuman Khandual wrote:
>> > Each individual node in the system has a ZONELIST_FALLBACK zonelist
>> > and a ZONELIST_NOFALLBACK zonelist. These zonelists decide fallback
>> > order of zones during memory allocations. Sometimes it helps to dump
>> > these zonelists to see the priority order of various zones in them.
>> >
>> > Particularly platforms which support memory hotplug into previously
>> > non existing zones (at boot), this interface helps in visualizing
>> > which all zonelists of the system at what priority level, the new
>> > hot added memory ends up in. POWER is such a platform where all the
>> > memory detected during boot time remains with ZONE_DMA for good but
>> > then hot plug process can actually get new memory into ZONE_MOVABLE.
>> > So having a way to get the snapshot of the zonelists on the system
>> > after memory or node hot[un]plug is desirable. This change adds one
>> > new sysfs interface (/sys/devices/system/memory/system_zone_details)
>> > which will fetch and dump this information.
> I am still not sure I understand why this is helpful and who is the
> consumer for this interface and how it will benefit from the
> information. Dave (who doesn't seem to be on the CC list re-added) had
> another objection that this breaks one-value-per-file rule for sysfs
> files.
It helps in understanding the relative priority of each memory zone of the
system during various allocation scenarios. Its particularly helpful after
hotplug/unplug of additional memory into previously non existing zone on
a node.
>
> This all smells like a debugging feature to me and so it should go into
> debugfs.
Sure, will make it a debugfs interface.
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WARNING: multiple messages have this Message-ID (diff)
From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>,
Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH V4] mm: Add sysfs interface to dump each node's zonelist information
Date: Mon, 12 Sep 2016 10:54:17 +0530 [thread overview]
Message-ID: <57D63C01.9090309@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160909133648.GL4844@dhcp22.suse.cz>
On 09/09/2016 07:06 PM, Michal Hocko wrote:
> On Thu 08-09-16 08:16:58, Anshuman Khandual wrote:
>> > Each individual node in the system has a ZONELIST_FALLBACK zonelist
>> > and a ZONELIST_NOFALLBACK zonelist. These zonelists decide fallback
>> > order of zones during memory allocations. Sometimes it helps to dump
>> > these zonelists to see the priority order of various zones in them.
>> >
>> > Particularly platforms which support memory hotplug into previously
>> > non existing zones (at boot), this interface helps in visualizing
>> > which all zonelists of the system at what priority level, the new
>> > hot added memory ends up in. POWER is such a platform where all the
>> > memory detected during boot time remains with ZONE_DMA for good but
>> > then hot plug process can actually get new memory into ZONE_MOVABLE.
>> > So having a way to get the snapshot of the zonelists on the system
>> > after memory or node hot[un]plug is desirable. This change adds one
>> > new sysfs interface (/sys/devices/system/memory/system_zone_details)
>> > which will fetch and dump this information.
> I am still not sure I understand why this is helpful and who is the
> consumer for this interface and how it will benefit from the
> information. Dave (who doesn't seem to be on the CC list re-added) had
> another objection that this breaks one-value-per-file rule for sysfs
> files.
It helps in understanding the relative priority of each memory zone of the
system during various allocation scenarios. Its particularly helpful after
hotplug/unplug of additional memory into previously non existing zone on
a node.
>
> This all smells like a debugging feature to me and so it should go into
> debugfs.
Sure, will make it a debugfs interface.
next prev parent reply other threads:[~2016-09-12 5:24 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-06 5:34 [PATCH V2 1/2] mm: Export definition of 'zone_names' array through mmzone.h Anshuman Khandual
2016-09-06 5:34 ` Anshuman Khandual
2016-09-06 5:34 ` [PATCH V2 2/2] mm: Add sysfs interface to dump each node's zonelist information Anshuman Khandual
2016-09-06 5:34 ` Anshuman Khandual
2016-09-06 6:11 ` kbuild test robot
2016-09-06 6:49 ` Anshuman Khandual
2016-09-06 6:49 ` Anshuman Khandual
2016-09-06 8:31 ` [PATCH V3] " Anshuman Khandual
2016-09-06 8:31 ` Anshuman Khandual
2016-09-06 9:05 ` kbuild test robot
2016-09-07 12:32 ` Anshuman Khandual
2016-09-07 12:32 ` Anshuman Khandual
2016-09-06 20:36 ` Dave Hansen
2016-09-06 20:36 ` Dave Hansen
2016-09-07 3:08 ` Kees Cook
2016-09-07 3:08 ` Kees Cook
2016-09-07 4:00 ` Anshuman Khandual
2016-09-07 4:00 ` Anshuman Khandual
2016-09-08 2:46 ` [PATCH V4] " Anshuman Khandual
2016-09-08 2:46 ` Anshuman Khandual
2016-09-08 7:44 ` kbuild test robot
2016-09-08 20:24 ` Dave Hansen
2016-09-08 20:24 ` Dave Hansen
2016-09-12 5:27 ` Anshuman Khandual
2016-09-12 5:27 ` Anshuman Khandual
2016-09-12 18:13 ` David Rientjes
2016-09-12 18:13 ` David Rientjes
2016-09-17 4:26 ` Anshuman Khandual
2016-09-17 4:26 ` Anshuman Khandual
2016-09-20 0:54 ` David Rientjes
2016-09-20 0:54 ` David Rientjes
2016-10-13 14:38 ` Anshuman Khandual
2016-10-13 14:38 ` Anshuman Khandual
2016-09-09 13:36 ` Michal Hocko
2016-09-09 13:36 ` Michal Hocko
2016-09-12 5:24 ` Anshuman Khandual [this message]
2016-09-12 5:24 ` Anshuman Khandual
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