Message ID | 20211112120208.74387-1-roger.pau@citrix.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [for-4.16,v2] Revert "domctl: improve locking during domain destruction" | expand |
Hi Roger, On 12/11/2021 12:02, Roger Pau Monne wrote: > This reverts commit 228ab9992ffb1d8f9d2475f2581e68b2913acb88. > > Performance analysis has shown that dropping the domctl lock during > domain destruction greatly increases the contention in the heap_lock, > thus making parallel destruction of domains slower. > > The following lockperf data shows the difference between the current > code and the reverted one: > > lock: 3342357(2.268295505s), block: 3263853(18.556650797s) > lock: 2788704(0.362311723s), block: 222681( 0.091152276s) > > Those figures are from Dmitry Isaikin, and are gathered after > destroying 5 2GB HVM guests in parallel: > > https://lists.xenproject.org/archives/html/xen-devel/2021-09/msg01515.html > > Given the current point in the release, revert the commit and > reinstate holding the domctl lock during domain destruction. Further > work should be done in order to re-add more fine grained locking to > the domain destruction path once a proper solution to avoid the > heap_lock contention is found. > > Reported-by: Hongyan Xia <hongyxia@amazon.com> > Reported-by: Dmitry Isaikin <isaikin-dmitry@yandex.ru> > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > Acked-by: Andrew Cooper <andrew.cooper3@citrix.com> Acked-by: Julien Grall <jgrall@amazon.com> Cheers,
diff --git a/xen/common/domain.c b/xen/common/domain.c index 56d47dd664..093bb4403f 100644 --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -917,21 +917,13 @@ int domain_kill(struct domain *d) if ( d == current->domain ) return -EINVAL; - /* Protected by d->domain_lock. */ + /* Protected by domctl_lock. */ switch ( d->is_dying ) { case DOMDYING_alive: - domain_unlock(d); domain_pause(d); - domain_lock(d); - /* - * With the domain lock dropped, d->is_dying may have changed. Call - * ourselves recursively if so, which is safe as then we won't come - * back here. - */ - if ( d->is_dying != DOMDYING_alive ) - return domain_kill(d); d->is_dying = DOMDYING_dying; + spin_barrier(&d->domain_lock); argo_destroy(d); vnuma_destroy(d->vnuma); domain_set_outstanding_pages(d, 0); diff --git a/xen/common/domctl.c b/xen/common/domctl.c index 271862ae58..879a2adcbe 100644 --- a/xen/common/domctl.c +++ b/xen/common/domctl.c @@ -497,14 +497,11 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl) break; case XEN_DOMCTL_destroydomain: - domctl_lock_release(); - domain_lock(d); ret = domain_kill(d); - domain_unlock(d); if ( ret == -ERESTART ) ret = hypercall_create_continuation( __HYPERVISOR_domctl, "h", u_domctl); - goto domctl_out_unlock_domonly; + break; case XEN_DOMCTL_setnodeaffinity: {