From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
To: Brijesh Singh <brijesh.s.singh@gmail.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] Mmap query
Date: Mon, 11 Oct 2021 22:38:40 +0300 [thread overview]
Message-ID: <20211011223840.32c95da3@sovereign> (raw)
In-Reply-To: <CAAQ1jEGTF=uOG=CeqZ1N8XD9i6DZgOHVw-fSQfDj7X27xNoi=w@mail.gmail.com>
Hi Brijesh,
2021-10-11 10:25 (UTC-0700), Brijesh Singh:
> Hi there,
> We are seeing high mmap time for 1G hugepage during eal memalloc init. Most
> time is spent for clearing page, each 4k size..
> It's not clear to me why clear huge pages is called? The code mmaps rte_map
> file with map_populate and map_shared this shouldn't cause page zeroing.
> I am curious to know how zeroing is forced?
The kernel clears all anonymous memory before handling it to the user space.
It is done for security: there may be sensitive data left by previous users
of those pages.
There is a pending patchset that aims to solve your issue:
https://mails.dpdk.org/archives/dev/2021-October/223723.html
Please see commit messages for some more explanations.
> As an alternative, I would like to memset from userspace. In my experiment
> we are noticing memset 1G file is faster that clear huge pages.
Can you share the numbers? From my experiments, mmap() is just a little
longer then memset() of the same amount of memory, apparently because the
kernel has some extra work to set up the mapping.
next prev parent reply other threads:[~2021-10-11 19:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-11 17:25 Brijesh Singh
2021-10-11 19:38 ` Dmitry Kozlyuk [this message]
2021-10-12 0:24 ` Brijesh Singh
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