Date: Fri, 20 Jun 2014 11:35:53 +0200 From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com> To: <virtualization@FreeBSD.org>, "freebsd-xen@freebsd.org" <freebsd-xen@freebsd.org>, <bryanv@FreeBSD.org> Subject: FreeBSD and memory balloon drivers Message-ID: <53A40079.9000804@citrix.com>
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Hello, I've been looking into the Xen balloon driver, because I've experienced problems when ballooning memory down which AFAICT are also present in the VirtIO balloon driver. The problem I've experienced is that when ballooning memory down, we basically allocate a bunch of memory as WIRED, to make sure nobody tries to swap it do disk, since it will crash the kernel because the memory is not populated. Due to this massive amount of memory allocated as WIRED, user-space programs that try to use mlock will fail because we hit the limit in vm.max_wired. I'm not sure what's the best way to deal with this limitation, should vm.max_wired be changed from the balloon drivers when ballooning down/up? Is there anyway to remove the pages ballooned down from the memory accounting of wired pages? Thanks, Roger.
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