2018-08-19 04:05:35

by Ocean He

Subject: [PATCH] libnvdimm, region_devs: stop NDD_ALIASING bit test if one test pass

From: Ocean He <[email protected]>

There is no need to finish entire loop to execute NDD_ALIASING bit test
against every nvdimm->flags. In practice, all the nd_mapping->nvdimm
have the same flags.

Because the check of alias is "if (alias)" but not
"if (alias == nd_region->ndr_mappings)", there is no function change while
just save a few cycles.

Signed-off-by: Ocean He <[email protected]>
---
A test to check if all the nd_mapping->nvdimm have the same flags, using
Lenovo ThinkSystem SR630 and 4.18-rc6.

# ipmctl show -dimm

DimmID Capacity HealthState ActionRequired LockState FWVersion
0x0021 125.7 GiB Healthy 0 Disabled 01.00.00.4888
0x0121 125.7 GiB Healthy 0 Disabled 01.00.00.4888
0x1021 125.7 GiB Healthy 0 Disabled 01.00.00.4888
0x1121 125.7 GiB Healthy 0 Disabled 01.00.00.4888

# ipmctl create -f -goal -socket 0x0 PersistentMemoryType=AppDirect

# ipmctl create -f -goal -socket 0x1 PersistentMemoryType=AppDirect

# reboot, to make goal configuration take effect.

# ndctl create-namespace -r region0 -s 100m -t pmem -m fsdax

# ndctl create-namespace -r region1 -s 100m -t pmem -m fsdax

# reboot and find all the nd_mapping->nvdimm have the same flags.

drivers/nvdimm/region_devs.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index ec3543b..fc3bc1c 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -234,8 +234,10 @@ int nd_region_to_nstype(struct nd_region *nd_region)
struct nd_mapping *nd_mapping = &nd_region->mapping[i];
struct nvdimm *nvdimm = nd_mapping->nvdimm;

- if (test_bit(NDD_ALIASING, &nvdimm->flags))
+ if (test_bit(NDD_ALIASING, &nvdimm->flags)) {
alias++;
+ break;
+ }
}
if (alias)
return ND_DEVICE_NAMESPACE_PMEM;
--
1.8.3.1

2018-08-30 21:56:50

by Verma, Vishal L

Subject: Re: [PATCH] libnvdimm, region_devs: stop NDD_ALIASING bit test if one test pass

On Sun, 2018-08-19 at 00:01 -0400, Ocean He wrote:
> From: Ocean He <[email protected]>
>
> There is no need to finish entire loop to execute NDD_ALIASING bit
> test
> against every nvdimm->flags. In practice, all the nd_mapping->nvdimm
> have the same flags.
>
> Because the check of alias is "if (alias)" but not
> "if (alias == nd_region->ndr_mappings)", there is no function change
> while
> just save a few cycles.
>
> Signed-off-by: Ocean He <[email protected]>
> ---
> A test to check if all the nd_mapping->nvdimm have the same flags,
> using
> Lenovo ThinkSystem SR630 and 4.18-rc6.
>
> # ipmctl show -dimm
>
> DimmID Capacity HealthState ActionRequired LockState
> FWVersion
> 0x0021 125.7
> GiB Healthy 0 Disabled 01.00.00.48
> 88
> 0x0121 125.7
> GiB Healthy 0 Disabled 01.00.00.48
> 88
> 0x1021 125.7
> GiB Healthy 0 Disabled 01.00.00.48
> 88
> 0x1121 125.7
> GiB Healthy 0 Disabled 01.00.00.48
> 88
>
> # ipmctl create -f -goal -socket 0x0 PersistentMemoryType=AppDirect
>
> # ipmctl create -f -goal -socket 0x1 PersistentMemoryType=AppDirect
>
> # reboot, to make goal configuration take effect.
>
> # ndctl create-namespace -r region0 -s 100m -t pmem -m fsdax
>
> # ndctl create-namespace -r region1 -s 100m -t pmem -m fsdax
>
> # reboot and find all the nd_mapping->nvdimm have the same flags.
>
> drivers/nvdimm/region_devs.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvdimm/region_devs.c
> b/drivers/nvdimm/region_devs.c
> index ec3543b..fc3bc1c 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -234,8 +234,10 @@ int nd_region_to_nstype(struct nd_region
> *nd_region)
> struct nd_mapping *nd_mapping = &nd_region-
> >mapping[i];
> struct nvdimm *nvdimm = nd_mapping->nvdimm;
>
> - if (test_bit(NDD_ALIASING, &nvdimm->flags))
> + if (test_bit(NDD_ALIASING, &nvdimm->flags))
> {
> alias++;
> + break;

I think we can go a step further, and instead of the 'break' followed
by a check for the 'alias' variable, in the loop, just return
ND_DEVICE_NAMESPACE_PMEM if the NDD_ALIASING bit is found for any
mapping. Outside the loop, simply return ND_DEVICE_NAMESPACE_IO. That
makes it much cleaner and now we can get rid of 'alias' entirely.

> + }
> }
> if (alias)
> return ND_DEVICE_NAMESPACE_PMEM;

2018-09-02 12:44:36

by Ocean HY1 He

Subject: RE: [External] Re: [PATCH] libnvdimm, region_devs: stop NDD_ALIASING bit test if one test pass

> -----Original Message-----
> From: Verma, Vishal L <[email protected]>
> Sent: Friday, August 31, 2018 5:51 AM
> To: Williams, Dan J <[email protected]>; [email protected];
> [email protected]; Jiang, Dave <[email protected]>
> Cc: [email protected]; [email protected]; Ocean HY1 He
> <[email protected]>
> Subject: [External] Re: [PATCH] libnvdimm, region_devs: stop NDD_ALIASING
> bit test if one test pass
>
>
> On Sun, 2018-08-19 at 00:01 -0400, Ocean He wrote:
> > From: Ocean He <[email protected]>
> >
> > There is no need to finish entire loop to execute NDD_ALIASING bit
> > test
> > against every nvdimm->flags. In practice, all the nd_mapping->nvdimm
> > have the same flags.
> >
> > Because the check of alias is "if (alias)" but not
> > "if (alias == nd_region->ndr_mappings)", there is no function change
> > while
> > just save a few cycles.
> >
> > Signed-off-by: Ocean He <[email protected]>
> > ---
> > A test to check if all the nd_mapping->nvdimm have the same flags,
> > using
> > Lenovo ThinkSystem SR630 and 4.18-rc6.
> >
> > # ipmctl show -dimm
> >
> > DimmID Capacity HealthState ActionRequired LockState
> > FWVersion
> > 0x0021 125.7
> > GiB Healthy 0 Disabled 01.00.00.48
> > 88
> > 0x0121 125.7
> > GiB Healthy 0 Disabled 01.00.00.48
> > 88
> > 0x1021 125.7
> > GiB Healthy 0 Disabled 01.00.00.48
> > 88
> > 0x1121 125.7
> > GiB Healthy 0 Disabled 01.00.00.48
> > 88
> >
> > # ipmctl create -f -goal -socket 0x0 PersistentMemoryType=AppDirect
> >
> > # ipmctl create -f -goal -socket 0x1 PersistentMemoryType=AppDirect
> >
> > # reboot, to make goal configuration take effect.
> >
> > # ndctl create-namespace -r region0 -s 100m -t pmem -m fsdax
> >
> > # ndctl create-namespace -r region1 -s 100m -t pmem -m fsdax
> >
> > # reboot and find all the nd_mapping->nvdimm have the same flags.
> >
> > drivers/nvdimm/region_devs.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/nvdimm/region_devs.c
> > b/drivers/nvdimm/region_devs.c
> > index ec3543b..fc3bc1c 100644
> > --- a/drivers/nvdimm/region_devs.c
> > +++ b/drivers/nvdimm/region_devs.c
> > @@ -234,8 +234,10 @@ int nd_region_to_nstype(struct nd_region
> > *nd_region)
> > struct nd_mapping *nd_mapping = &nd_region-
> > >mapping[i];
> > struct nvdimm *nvdimm = nd_mapping->nvdimm;
> >
> > - if (test_bit(NDD_ALIASING, &nvdimm->flags))
> > + if (test_bit(NDD_ALIASING, &nvdimm->flags))
> > {
> > alias++;
> > + break;
>
> I think we can go a step further, and instead of the 'break' followed
> by a check for the 'alias' variable, in the loop, just return
> ND_DEVICE_NAMESPACE_PMEM if the NDD_ALIASING bit is found for any
> mapping. Outside the loop, simply return ND_DEVICE_NAMESPACE_IO. That
> makes it much cleaner and now we can get rid of 'alias' entirely.
>
Hi Vishal,

Thanks for comments and I would send version 2 patch later.

Ocean.
> > + }
> > }
> > if (alias)
> > return ND_DEVICE_NAMESPACE_PMEM;