diff options
| author | Juergen Gross <jgross@suse.com> | 2017-06-12 13:53:56 +0200 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2017-06-25 13:11:27 +0200 |
| commit | a5d5f328b0e2baa5ee7c119fd66324eb79eeeb66 (patch) | |
| tree | 7a56d9ab6a01a47a8b758f90b5cbfee96461f10d /arch/x86/xen/enlighten_pv.c | |
| parent | 1a3fc2c402810bf336882e695abd1678dbc8d279 (diff) | |
xen: allocate page for shared info page from low memory
In a HVM guest the kernel allocates the page for mapping the shared
info structure via extend_brk() today. This will lead to a drop of
performance as the underlying EPT entry will have to be split up into
4kB entries as the single shared info page is located in hypervisor
memory.
The issue has been detected by using the libmicro munmap test:
unmapping 8kB of memory was faster by nearly a factor of two when no
pv interfaces were active in the HVM guest.
So instead of taking a page from memory which might be mapped via
large EPT entries use a page which is already mapped via a 4kB EPT
entry: we can take a page from the first 1MB of memory as the video
memory at 640kB disallows using larger EPT entries.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'arch/x86/xen/enlighten_pv.c')
| -rw-r--r-- | arch/x86/xen/enlighten_pv.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index bc44d2175459..811e4ddb3f37 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -89,8 +89,6 @@ void *xen_initial_gdt; -RESERVE_BRK(shared_info_page_brk, PAGE_SIZE); - static int xen_cpu_up_prepare_pv(unsigned int cpu); static int xen_cpu_dead_pv(unsigned int cpu); |