On 09/14/2015 11:58 PM, Dmitry Stogov wrote: > On Tue, Sep 15, 2015 at 4:31 AM, Rasmus Lerdorf <ras...@lerdorf.com > <mailto:ras...@lerdorf.com>> wrote: > Redhat enables THP by default and has for a while, but I know lots of > admins that disable this feature right away on production machines. I > don't think it is default on Ubuntu, but at least they have hugepage > tools to make it easy to configure. And from a quick look at Debnian > (jessie) it wasn't obvious how to get hugepages working. I don't see a > package for hugeadm offhand. The kernel supports it, obviously, but you > need to take some steps to configure them. > > > PHP prefers using regular Huge Pages and may fail back to THP > (Transparent Huge Pages). > So THP don't have to be enabled. > > > > Which means we also need to spend a bit of time documenting how to > enable hugepages at the OS level for the various operating systems to go > along with this feature. > > > Right. Manual OS configuration is required. See > https://wiki.debian.org/Hugepages#Enabling_HugeTlbPage > Steps (3) and (4) are optional.
Yup. I did get it working here. Perhaps it would be a good idea to add a row to the phpinfo() OpCache section indicating whether huge pages are currently being used. It would make it easier to debug. I know you can check /proc/meminfo directly, but it isn't obvious what exactly is using the hugepages from that. -Rasmus
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