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From: "Qiu, Michael" <michael.qiu@intel.com>
To: Jay Rolette <rolette@infiniteio.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] Avoid possible memory cpoy when sort	hugepages
Date: Thu, 11 Dec 2014 01:44:55 +0000
Message-ID: <533710CFB86FA344BFBF2D6802E60286C9EA4B@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <CADNuJVpsNNOymFmmCPGA9hHB84bzT-N90mci6j5YZqVKtCfi3Q@mail.gmail.com>

On 12/11/2014 5:37 AM, Jay Rolette wrote:
> On Wed, Dec 10, 2014 at 12:39 PM, Ananyev, Konstantin <
> konstantin.ananyev@intel.com> wrote:
>
>>> I just got through replacing that entire function in my repo with a call
>> to qsort() from the standard library last night myself. Faster
>>> (although probably not material to most deployments) and less code.
>> If you feel like it is worth it, why not to submit a patch? :)
>
> On Haswell and IvyBridge Xeons, with 128 1G huge pages, it doesn't make a
> user-noticeable difference in the time required for
> rte_eal_hugepage_init(). The reason I went ahead and checked it in my repo
> is because:
>
> a) it eats at my soul to see an O(n^2) case for something where qsort() is
> trivial to use
> b) we will increase that up to ~232 1G huge pages soon. Likely doesn't
> matter at that point either, but since it was already written...
>
> What *does* chew up a lot of time in init is where the huge pages are being
> explicitly zeroed in map_all_hugepages().
>
> Removing that memset() makes find_numasocket() blow up, but I was able to
> do a quick test where I only memset 1 byte on each page. That cut init time
> by 30% (~20 seconds in my test).  Significant, but since I'm not entirely
> sure it is safe, I'm not making that change right now.
>
> On Linux, shared memory that isn't file-backed is automatically zeroed
> before the app gets it. However, I haven't had a chance to chase down
> whether that applies to huge pages or not, much less how hugetlbfs factors
> into the equation.
>
> Back to the question about the patch, if you guys are interested in it,
> I'll have to figure out your patch submission process. Shouldn't be a huge
> deal other than the fact that we are on DPDK 1.6 (r2).

Go ahead and post it :)

Thanks,
Michael
> Cheers,
> Jay
>


      reply	other threads:[~2014-12-11  1:45 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-10  2:25 Michael Qiu
2014-12-10 10:41 ` Bruce Richardson
2014-12-10 10:59   ` Qiu, Michael
2014-12-10 11:08     ` Ananyev, Konstantin
2014-12-10 17:58       ` Jay Rolette
     [not found]         ` <2601191342CEEE43887BDE71AB977258213BED0C@IRSMSX105.ger.corp.intel.com>
2014-12-10 18:39           ` Ananyev, Konstantin
2014-12-10 21:36             ` Jay Rolette
2014-12-11  1:44               ` Qiu, Michael [this message]

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