Re: Hugepages - benefits / drawbacks
- From: David Miller <David.J.Miller@xxxxxxx>
- To: Christo Kutrovsky <kutrovsky.oracle@xxxxxxxxx>
- Date: Fri, 10 Oct 2008 10:28:26 -0500
Hi Christo,
This can be a problem, depending on the size of the SGA and the amount of
memory. There is a process that is responsible for reconstructing large
pages from smaller ones but there are situations where it either can't work
fast enough or can't relocate the necessary pages to do so. To make a
single 4M page, the right 512 8K pages have to all be available, since the
memory addresses have to be contiguous. Copying files tends to use a lot of
filesystem buffers, which are usually 8K and so may break up many 4M
pages. Those then have to be coalesced to provide 4M pages to the application
afterwards. There are some workarounds that can help that happen and later
versions of Solaris 10 do a better job of this, but it still can be an issue.
Regards,
Dave Miller
Christo Kutrovsky wrote, On 10/09/08 16:05:
However the problem with Solaris is if you have the database down
while you do ...say file copy operations, then the memory gets
fragmented and when you start it up later it's using smaller pages /
less of the "large" pages.
However, this is not an issue on Solaris at all due to ISM.
--
//www.freelists.org/webpage/oracle-l
Other related posts:
