| Message ID | 1457604443-32344-1-git-send-email-rcojocaru@bitdefender.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
>>> On 10.03.16 at 11:07, <rcojocaru@bitdefender.com> wrote: > Currently REP emulations optimizations remain disabled even if > the emulation does not happen as a result of a vm_event reply > requestion emulation (i.e. even for regular IO). This patch takes > emulate_each_rep into account only if emulation has been requested > by a vm_event-capable application, and is a noticeable speed > optimization for monitored guests. > > Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com> Looks reasonable, but this being an event specific change I'm making my ack to this dependent on Tamas'es consent. Jan > --- a/xen/arch/x86/hvm/emulate.c > +++ b/xen/arch/x86/hvm/emulate.c > @@ -498,6 +498,7 @@ static int hvmemul_virtual_to_linear( > { > struct segment_register *reg; > int okay; > + unsigned long max_reps = 4096; > > if ( seg == x86_seg_none ) > { > @@ -506,16 +507,21 @@ static int hvmemul_virtual_to_linear( > } > > /* > + * If introspection has been enabled for this domain, and we're emulating > + * becase a vm_reply asked us to (i.e. not doing regular IO) reps should > + * be at most 1, since optimization might otherwise cause a single > + * vm_event being triggered for repeated writes to a whole page. > + */ > + if ( unlikely(current->domain->arch.mem_access_emulate_each_rep) && > + current->arch.vm_event->emulate_flags != 0 ) > + max_reps = 1; > + > + /* > * Clip repetitions to avoid overflow when multiplying by @bytes_per_rep. > * The chosen maximum is very conservative but it's what we use in > * hvmemul_linear_to_phys() so there is no point in using a larger value. > - * If introspection has been enabled for this domain, *reps should be > - * at most 1, since optimization might otherwise cause a single vm_event > - * being triggered for repeated writes to a whole page. > */ > - *reps = min_t(unsigned long, *reps, > - unlikely(current->domain->arch.mem_access_emulate_each_rep) > - ? 1 : 4096); > + *reps = min_t(unsigned long, *reps, max_reps); > > reg = hvmemul_get_seg_reg(seg, hvmemul_ctxt); > > -- > 1.9.1
On 10/03/16 10:07, Razvan Cojocaru wrote: > Currently REP emulations optimizations remain disabled even if > the emulation does not happen as a result of a vm_event reply > requestion emulation (i.e. even for regular IO). This patch takes > emulate_each_rep into account only if emulation has been requested > by a vm_event-capable application, and is a noticeable speed > optimization for monitored guests. > > Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
On Mar 10, 2016 11:09, "Razvan Cojocaru" <rcojocaru@bitdefender.com> wrote: > > Currently REP emulations optimizations remain disabled even if > the emulation does not happen as a result of a vm_event reply > requestion emulation (i.e. even for regular IO). This patch takes > emulate_each_rep into account only if emulation has been requested > by a vm_event-capable application, and is a noticeable speed > optimization for monitored guests. > > Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com> Reviewed-by: Tamas K Lengyel <tamas@tklengyel.com> > --- > xen/arch/x86/hvm/emulate.c | 18 ++++++++++++------ > 1 file changed, 12 insertions(+), 6 deletions(-) > > diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c > index 082aa30..ddc8007 100644 > --- a/xen/arch/x86/hvm/emulate.c > +++ b/xen/arch/x86/hvm/emulate.c > @@ -498,6 +498,7 @@ static int hvmemul_virtual_to_linear( > { > struct segment_register *reg; > int okay; > + unsigned long max_reps = 4096; > > if ( seg == x86_seg_none ) > { > @@ -506,16 +507,21 @@ static int hvmemul_virtual_to_linear( > } > > /* > + * If introspection has been enabled for this domain, and we're emulating > + * becase a vm_reply asked us to (i.e. not doing regular IO) reps should > + * be at most 1, since optimization might otherwise cause a single > + * vm_event being triggered for repeated writes to a whole page. > + */ > + if ( unlikely(current->domain->arch.mem_access_emulate_each_rep) && > + current->arch.vm_event->emulate_flags != 0 ) > + max_reps = 1; > + > + /* > * Clip repetitions to avoid overflow when multiplying by @bytes_per_rep. > * The chosen maximum is very conservative but it's what we use in > * hvmemul_linear_to_phys() so there is no point in using a larger value. > - * If introspection has been enabled for this domain, *reps should be > - * at most 1, since optimization might otherwise cause a single vm_event > - * being triggered for repeated writes to a whole page. > */ > - *reps = min_t(unsigned long, *reps, > - unlikely(current->domain->arch.mem_access_emulate_each_rep) > - ? 1 : 4096); > + *reps = min_t(unsigned long, *reps, max_reps); > > reg = hvmemul_get_seg_reg(seg, hvmemul_ctxt); > > -- > 1.9.1 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c index 082aa30..ddc8007 100644 --- a/xen/arch/x86/hvm/emulate.c +++ b/xen/arch/x86/hvm/emulate.c @@ -498,6 +498,7 @@ static int hvmemul_virtual_to_linear( { struct segment_register *reg; int okay; + unsigned long max_reps = 4096; if ( seg == x86_seg_none ) { @@ -506,16 +507,21 @@ static int hvmemul_virtual_to_linear( } /* + * If introspection has been enabled for this domain, and we're emulating + * becase a vm_reply asked us to (i.e. not doing regular IO) reps should + * be at most 1, since optimization might otherwise cause a single + * vm_event being triggered for repeated writes to a whole page. + */ + if ( unlikely(current->domain->arch.mem_access_emulate_each_rep) && + current->arch.vm_event->emulate_flags != 0 ) + max_reps = 1; + + /* * Clip repetitions to avoid overflow when multiplying by @bytes_per_rep. * The chosen maximum is very conservative but it's what we use in * hvmemul_linear_to_phys() so there is no point in using a larger value. - * If introspection has been enabled for this domain, *reps should be - * at most 1, since optimization might otherwise cause a single vm_event - * being triggered for repeated writes to a whole page. */ - *reps = min_t(unsigned long, *reps, - unlikely(current->domain->arch.mem_access_emulate_each_rep) - ? 1 : 4096); + *reps = min_t(unsigned long, *reps, max_reps); reg = hvmemul_get_seg_reg(seg, hvmemul_ctxt);
Currently REP emulations optimizations remain disabled even if the emulation does not happen as a result of a vm_event reply requestion emulation (i.e. even for regular IO). This patch takes emulate_each_rep into account only if emulation has been requested by a vm_event-capable application, and is a noticeable speed optimization for monitored guests. Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com> --- xen/arch/x86/hvm/emulate.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)