DPDK patches and discussions
 help / color / mirror / Atom feed
From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: dev@dpdk.org, John McNamara <john.mcnamara@intel.com>,
	Marko Kovacevic <marko.kovacevic@intel.com>,
	ferruh.yigit@intel.com, padraig.j.connolly@intel.com,
	stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 2/2] doc/linux_gsg: update information on using hugepages
Date: Tue, 25 Aug 2020 10:28:53 +0100
Message-ID: <f9aa59e3-2f51-a5c3-e404-423d78dfb56e@intel.com> (raw)
In-Reply-To: <20200824171307.GE547@bricha3-MOBL.ger.corp.intel.com>

On 24-Aug-20 6:13 PM, Bruce Richardson wrote:
> On Mon, Aug 24, 2020 at 04:45:01PM +0100, Anatoly Burakov wrote:
>> Current information regarding hugepage usage is a little out of date.
>> Update it to include information on in-memory mode, as well as on
>> default mountpoints provided by systemd.
>>
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
>> ---
>>   doc/guides/linux_gsg/sys_reqs.rst | 39 +++++++++++++++++++------------
>>   1 file changed, 24 insertions(+), 15 deletions(-)
>>
>> diff --git a/doc/guides/linux_gsg/sys_reqs.rst b/doc/guides/linux_gsg/sys_reqs.rst
>> index a124656bcb..2ddd7ed667 100644
>> --- a/doc/guides/linux_gsg/sys_reqs.rst
>> +++ b/doc/guides/linux_gsg/sys_reqs.rst
>> @@ -155,8 +155,12 @@ Without hugepages, high TLB miss rates would occur with the standard 4k page siz
>>   Reserving Hugepages for DPDK Use
>>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>   
>> -The allocation of hugepages should be done at boot time or as soon as possible after system boot
>> -to prevent memory from being fragmented in physical memory.
>> +The allocation of hugepages can be performed either at run time or at boot time.
>> +In the general case, reserving hugepages at run time is perfectly fine, but in
>> +use cases where having lots of physically contiguous memory is required, it is
>> +preferable to reserve hugepages at boot time, as that will help in preventing
>> +physical memory from becoming heavily fragmented.
>> +
> 
> Although we are removing the note about 1G pages requiring to be reserved
> at boot time, I think we should still mention here that some older kernel
> versions do not allow 1G reservations post-boot.

Agreed, will fix in v2.

> 
>>   To reserve hugepages at boot time, a parameter is passed to the Linux kernel on the kernel command line.
>>   
>>   For 2 MB pages, just pass the hugepages option to the kernel. For example, to reserve 1024 pages of 2 MB, use::
>> @@ -187,9 +191,9 @@ See the Documentation/admin-guide/kernel-parameters.txt file in your Linux sourc
>>   
>>   **Alternative:**
>>   
>> -For 2 MB pages, there is also the option of allocating hugepages after the system has booted.
>> +There is also the option of allocating hugepages after the system has booted.
>>   This is done by echoing the number of hugepages required to a nr_hugepages file in the ``/sys/devices/`` directory.
>> -For a single-node system, the command to use is as follows (assuming that 1024 pages are required)::
>> +For a single-node system, the command to use is as follows (assuming that 1024 of 2MB pages are required)::
>>   
>>       echo 1024 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
>>   
>> @@ -198,22 +202,27 @@ On a NUMA machine, pages should be allocated explicitly on separate nodes::
>>       echo 1024 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
>>       echo 1024 > /sys/devices/system/node/node1/hugepages/hugepages-2048kB/nr_hugepages
>>   
>> -.. note::
>> -
>> -    For 1G pages, it is not possible to reserve the hugepage memory after the system has booted.
>> -
>>   Using Hugepages with the DPDK
>>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>   
>> -Once the hugepage memory is reserved, to make the memory available for DPDK use, perform the following steps::
>> +If secondary process support is not required, DPDK is able to use hugepages
>> +without any configuration by using "in-memory" mode. Please see
>> +:ref:`linux_eal_parameters` for more details.
>> +
>> +If secondary process support is required, mount points for hugepages need to be
>> +created. On modern Linux distributions, a default mount point for hugepages is provided
>> +by the system and is located at ``/dev/hugepages``. This mount point will use the
>> +default hugepage size set by the kernel parameters as described above.
>> +
>> +However, in order to use multiple hugepage sizes, it is necessary to manually
> 
> Rather than multiple hugepage sizes, I'd suggest changing this to hugepage
> sizes other than the default.

OK, will fix.

> 
> Do we also want to add a line somewhere explaining that the default size
> can be set a boot using a kernel parameter?

It's already there, right above this :)

> 
>> +create mount points for hugepage sizes that are not provided by the system
>> +(e.g. 1GB pages).
>> +
>> +To make the hugepages of size 1GB available for DPDK use, perform the following steps::
>>   
>>       mkdir /mnt/huge
>> -    mount -t hugetlbfs nodev /mnt/huge
>> +    mount -t hugetlbfs pagesize=1GB /mnt/huge
>>   
>>   The mount point can be made permanent across reboots, by adding the following line to the ``/etc/fstab`` file::
>>   
>> -    nodev /mnt/huge hugetlbfs defaults 0 0
>> -
>> -For 1GB pages, the page size must be specified as a mount option::
>> -
>> -    nodev /mnt/huge_1GB hugetlbfs pagesize=1GB 0 0
>> +    nodev /mnt/huge hugetlbfs pagesize=1GB 0 0
>> -- 
>> 2.17.1


-- 
Thanks,
Anatoly

  reply	other threads:[~2020-08-25  9:29 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-24 15:45 [dpdk-dev] [PATCH 1/2] doc/linux_gsg: clarify instructions on running as non-root Anatoly Burakov
2020-08-24 15:45 ` [dpdk-dev] [PATCH 2/2] doc/linux_gsg: update information on using hugepages Anatoly Burakov
2020-08-24 17:13   ` Bruce Richardson
2020-08-25  9:28     ` Burakov, Anatoly [this message]
2020-08-24 17:08 ` [dpdk-dev] [PATCH 1/2] doc/linux_gsg: clarify instructions on running as non-root Bruce Richardson
2020-08-25  9:29   ` Burakov, Anatoly
2020-08-25  7:47 ` Ferruh Yigit
2020-08-25 12:17 ` [dpdk-dev] [PATCH v2 " Anatoly Burakov
2020-08-25 13:06   ` Bruce Richardson
2020-08-25 13:57   ` [dpdk-dev] [PATCH v3 " Anatoly Burakov
2020-11-19 10:52     ` [dpdk-dev] [PATCH v4 1/2] doc: " Anatoly Burakov
2020-11-19 10:52     ` [dpdk-dev] [PATCH v4 2/2] doc/linux_gsg: update information on using hugepages Anatoly Burakov
2020-11-19 21:03       ` David Marchand
2020-11-20 10:50         ` Burakov, Anatoly
2020-11-27 15:23       ` [dpdk-dev] [dpdk-stable] " Thomas Monjalon
2020-08-25 13:57   ` [dpdk-dev] [PATCH v3 " Anatoly Burakov
2020-08-25 12:17 ` [dpdk-dev] [PATCH v2 " Anatoly Burakov
2020-08-25 13:10   ` Bruce Richardson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=f9aa59e3-2f51-a5c3-e404-423d78dfb56e@intel.com \
    --to=anatoly.burakov@intel.com \
    --cc=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    --cc=ferruh.yigit@intel.com \
    --cc=john.mcnamara@intel.com \
    --cc=marko.kovacevic@intel.com \
    --cc=padraig.j.connolly@intel.com \
    --cc=stable@dpdk.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git