[pve-devel] [PATCH 1/2] add hugepages option

[Alexandre DERUMIER]

>>Normally hugepages are setup via sysctl.conf. Default size is always 2 MB. No need for kernel commandline editing. 

for 2MB yes, for 1GB hugepage I'm not sure you can enable them through sysctl

>>Why exactly are you using hugepages? 
needed for ovs + vhost-user + dpdk

>>Can KVM handle hugepages? Normally hugepages implies no KSM, isn't that right? 

yes sure , it can handle it. Memory is preallocated at vm start, so KSM can't work here



----- Mail original -----
De: "Andreas Steinel" <a.steinel at gmail.com>
À: "dietmar" <dietmar at proxmox.com>, "pve-devel" <pve-devel at pve.proxmox.com>
Cc: "aderumier" <aderumier at odiso.com>
Envoyé: Jeudi 12 Mai 2016 13:30:08
Objet: Re: [pve-devel] [PATCH 1/2] add hugepages option

Normally hugepages are setup via sysctl.conf. Default size is always 2 MB. No need for kernel commandline editing. 
Why exactly are you using hugepages? Can KVM handle hugepages? Normally hugepages implies no KSM, isn't that right? 

On Thu, May 12, 2016 at 12:57 PM, Dietmar Maurer < dietmar at proxmox.com > wrote: 


> host configuration 
> ------------------ 
> hugepages need to be allocated at boot 
> 
> for 4GB of 2M hugepages 
> 
> /etc/default/grub 
> ----------------- 
> GRUB_CMDLINE_LINUX_DEFAULT="quiet hugepagesz=2M hugepages=2048" 
> 
> /etc/fstab 
> ---------- 
> hugetlbfs /dev/hugepages hugetlbfs pagesize=2048k 0 0 
> 
> for 4GB for 1GB hugepages 
> 
> /etc/default/grub 
> ----------------- 
> GRUB_CMDLINE_LINUX_DEFAULT="quiet default_hugepagesz=1G hugepagesz=1G 
> hugepages=4" 

It is still unclear to me how to setup hugepages. On my host /dev/hugepages 
is already mounted: 

# mount|grep hugecgroup on /sys/fs/cgroup/hugetlb type cgroup 
(rw,nosuid,nodev,noexec,relatime,hugetlb,release_agent=/run/cgmanager/agents/cgm-release-agent.hugetlb,nsroot=/) 
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime) 
hugetlb on /run/lxcfs/controllers/hugetlb type cgroup 
(rw,relatime,hugetlb,release_agent=/run/cgmanager/agents/cgm-release-agent.hugetlb,nsroot=/) 

who mount that? Do I still need above setup? How do I know the number 
of required hugepages in advance? How can we make that more convenient for 
the user? 

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