From: "Alkalay, Amitai" <Amitai.Alkalay@emc.com>
To: "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: kernel mem_map reservation with hugepages
Date: Thu, 12 Jun 2014 17:47:42 -0400 [thread overview]
Message-ID: <E01DC0E960CD0F49B63BFEE7FBA569971125F1D1C0@MX16A.corp.emc.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 753 bytes --]
Hi,
According to this page<http://linux-mm.org/WhereDidMyMemoryGo> about 1.36% of the system memory is reserved to mem_map (I confirmed it before in the code - I saw that the kernel indeed saves a struct of 65 bytes for each page, meaning 63 structs per page).
I have a server (CentOS6) with 256GB of RAM, so it means that the kernel reserves about 4GB for mem_map.
Most of the pages in my server are hugepages, using the kernel command line argument "hugepages=X".
I believe this means that the kernel can reserve a much smaller amount of memory for the mappings - since there are much less pages (i.e. if all pages are huges it can reserve 8MB instead of 4GB).
Am I right?
Any suggestions if and how it can be done?
Thanks,
Amitai
[-- Attachment #2: Type: text/html, Size: 3071 bytes --]
reply other threads:[~2014-06-12 21:48 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
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=E01DC0E960CD0F49B63BFEE7FBA569971125F1D1C0@MX16A.corp.emc.com \
--to=amitai.alkalay@emc.com \
--cc=linux-mm@kvack.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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox