[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen master] x86/PoD: tighten conditions for checking super page
commit 513c203a0046232c55adf6d70ec1dbe54e8d157f Author: Jan Beulich <jbeulich@xxxxxxxx> AuthorDate: Fri Nov 20 12:37:37 2015 +0100 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Fri Nov 20 12:37:37 2015 +0100 x86/PoD: tighten conditions for checking super page Since calling the function isn't cheap, try to avoid the call when we know up front it won't help; see the code comment for details on those conditions. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx> --- xen/arch/x86/mm/p2m-pod.c | 22 +++++++++++++--------- 1 files changed, 13 insertions(+), 9 deletions(-) diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c index be15cf3..5d23b0d 100644 --- a/xen/arch/x86/mm/p2m-pod.c +++ b/xen/arch/x86/mm/p2m-pod.c @@ -528,7 +528,6 @@ p2m_pod_decrease_reservation(struct domain *d, if ( unlikely(d->is_dying) ) goto out_unlock; -recount: pod = nonpod = ram = 0; /* Figure out if we need to steal some freed memory for our cache */ @@ -568,15 +567,20 @@ recount: goto out_entry_check; } - /* Try to grab entire superpages if possible. Since the common case is for drivers - * to pass back singleton pages, see if we can take the whole page back and mark the - * rest PoD. */ - if ( steal_for_cache - && p2m_pod_zero_check_superpage(p2m, gpfn & ~(SUPERPAGE_PAGES-1))) + /* + * Try to grab entire superpages if possible. Since the common case is for + * drivers to pass back singleton pages, see if we can take the whole page + * back and mark the rest PoD. + * No need to do this though if + * - order >= SUPERPAGE_ORDER (the loop below will take care of this) + * - not all of the pages were RAM (now knowing order < SUPERPAGE_ORDER) + */ + if ( steal_for_cache && order < SUPERPAGE_ORDER && ram == (1 << order) && + p2m_pod_zero_check_superpage(p2m, gpfn & ~(SUPERPAGE_PAGES - 1)) ) { - /* Since order may be arbitrary, we may have taken more or less - * than we were actually asked to; so just re-count from scratch */ - goto recount; + pod = 1 << order; + ram = nonpod = 0; + ASSERT(steal_for_cache == (p2m->pod.entry_count > p2m->pod.count)); } /* Process as long as: -- generated by git-patchbot for /home/xen/git/xen.git#master _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx http://lists.xensource.com/xen-changelog
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |