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Date: Thu, 30 Aug 2018 21:51:01 +0000 From: "Verma, Vishal L" <vishal.l.verma@...el.com> To: "Williams, Dan J" <dan.j.williams@...el.com>, "ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>, "oceanhehy@...il.com" <oceanhehy@...il.com>, "Jiang, Dave" <dave.jiang@...el.com> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>, "hehy1@...ovo.com" <hehy1@...ovo.com> 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 <hehy1@...ovo.com> > > 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 <hehy1@...ovo.com> > --- > 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;
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