DPDK patches and discussions
 help / color / mirror / Atom feed
From: Alejandro Lucero <alejandro.lucero@netronome.com>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>
Cc: dev <dev@dpdk.org>, dpdk stable <stable@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 17.11] mem: fix memory initialization time
Date: Fri, 16 Nov 2018 14:42:55 +0000
Message-ID: <CAD+H992sDbY77ajcNaeF5oYsU5=R-mjTiC3VG748GLZX3kxkTQ@mail.gmail.com> (raw)
In-Reply-To: <431aff9c-4d26-8c81-04d4-49b274c13ee1@intel.com>

On Fri, Nov 16, 2018 at 1:35 PM Burakov, Anatoly <anatoly.burakov@intel.com>
wrote:

> On 16-Nov-18 12:49 PM, Alejandro Lucero wrote:
> >
> >
> > On Thu, Nov 15, 2018 at 1:16 PM Burakov, Anatoly
> > <anatoly.burakov@intel.com <mailto:anatoly.burakov@intel.com>> wrote:
> >
> >     On 12-Nov-18 11:18 AM, Alejandro Lucero wrote:
> >      > When using large amount of hugepage based memory, doing all the
> >      > hugepages mapping can take quite significant time.
> >      >
> >      > The problem is hugepages being initially mmaped to virtual
> addresses
> >      > which will be tried later for the final hugepage mmaping. This
> causes
> >      > the final mapping requiring calling mmap with another hint
> >     address which
> >      > can happen several times, depending on the amount of memory to
> >     mmap, and
> >      > which each mmmap taking more than a second.
> >      >
> >      > This patch changes the hint for the initial hugepage mmaping using
> >      > a starting address which will not collide with the final mmaping.
> >      >
> >      > Fixes: 293c0c4b957f ("mem: use address hint for mapping
> hugepages")
> >      >
> >      > Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com
> >     <mailto:alejandro.lucero@netronome.com>>
> >      > ---
> >
> >     Hi Alejandro,
> >
> >     I'm not sure i understand the purpose. When final mapping is
> performed,
> >     we reserve new memory area, and map pages into it. (i don't quite
> >     understand why we unmap the area before mapping pages, but it's how
> >     it's
> >     always been and i didn't change it in the legacy code)
> >
> >     Which addresses are causing the collision?
> >
> >
> > Because the hint for the final mapping is at 4GB address, and the
> > hugepages are initially individually mapped starting at low virtual
> > addresses, when the memory to map is 4GB or higher, the hugepages will
> > end using that hint address and higher. The more the hugepages to mmap,
> > the more addresses above the hint address are used, and the more mmaps
> > failed for getting the virtual addresses for the final mmap.
>
> Yes, but i still don't understand what the problem is.
>
> Before the final mapping, all of the pages get unmapped. They no longer
> occupy any VA space at all. Then, we create a VA-area the size of
> IOVA-contiguous chunk we have, but then we also unmap *that* (again, no
> idea why we actually do that, but that's how it works). So, the final
> mapping is performed with the knowledge that there are no pages at
> specified addresses, and mapping for specified addresses is performed
> when the first mapping has already been unmapped.
>
> As far as i understand, at no point do we hold addresses for initial and
> final mappings concurrently. So, where does the conflict come in?
>
>
Are you sure about this? Because I can see calling unmap_all_hugepage_init
happens after the second call to map_all_hugepages.

Maybe you are looking at the legacy code in a newer version which is not
exactly doing the same steps.


> >
> >     --
> >     Thanks,
> >     Anatoly
> >
>
>
> --
> Thanks,
> Anatoly
>

  reply	other threads:[~2018-11-16 14:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-12 11:18 Alejandro Lucero
2018-11-12 11:26 ` [dpdk-dev] [dpdk-stable] " Eelco Chaudron
2018-11-14 12:45   ` Eelco Chaudron
2018-11-15 13:16 ` [dpdk-dev] " Burakov, Anatoly
2018-11-16 12:49   ` Alejandro Lucero
2018-11-16 13:35     ` Burakov, Anatoly
2018-11-16 14:42       ` Alejandro Lucero [this message]
2018-11-16 15:56         ` Burakov, Anatoly

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='CAD+H992sDbY77ajcNaeF5oYsU5=R-mjTiC3VG748GLZX3kxkTQ@mail.gmail.com' \
    --to=alejandro.lucero@netronome.com \
    --cc=anatoly.burakov@intel.com \
    --cc=dev@dpdk.org \
    --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