From: Keith Busch <keith.busch@intel.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Rafael Wysocki <rafael@kernel.org>,
"Hansen, Dave" <dave.hansen@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>
Subject: Re: [PATCH 4/7] node: Add memory caching attributes
Date: Mon, 26 Nov 2018 12:53:53 -0700 [thread overview]
Message-ID: <20181126195352.GS26707@localhost.localdomain> (raw)
In-Reply-To: <20181126190619.GA32595@kroah.com>
On Mon, Nov 26, 2018 at 11:06:19AM -0800, Greg Kroah-Hartman wrote:
> On Wed, Nov 14, 2018 at 03:49:17PM -0700, Keith Busch wrote:
> > System memory may have side caches to help improve access speed. While
> > the system provided cache is transparent to the software accessing
> > these memory ranges, applications can optimize their own access based
> > on cache attributes.
> >
> > In preparation for such systems, provide a new API for the kernel to
> > register these memory side caches under the memory node that provides it.
> >
> > The kernel's sysfs representation is modeled from the cpu cacheinfo
> > attributes, as seen from /sys/devices/system/cpu/cpuX/cache/. Unlike CPU
> > cacheinfo, though, a higher node's memory cache level is nearer to the
> > CPU, while lower levels are closer to the backing memory. Also unlike
> > CPU cache, the system handles flushing any dirty cached memory to the
> > last level the memory on a power failure if the range is persistent.
> >
> > The exported attributes are the cache size, the line size, associativity,
> > and write back policy.
> >
> > Signed-off-by: Keith Busch <keith.busch@intel.com>
> > ---
> > drivers/base/node.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/node.h | 23 ++++++++++
> > 2 files changed, 140 insertions(+)
> >
> > diff --git a/drivers/base/node.c b/drivers/base/node.c
> > index 232535761998..bb94f1d18115 100644
> > --- a/drivers/base/node.c
> > +++ b/drivers/base/node.c
> > @@ -60,6 +60,12 @@ static DEVICE_ATTR(cpumap, S_IRUGO, node_read_cpumask, NULL);
> > static DEVICE_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL);
> >
> > #ifdef CONFIG_HMEM
> > +struct node_cache_obj {
> > + struct kobject kobj;
> > + struct list_head node;
> > + struct node_cache_attrs cache_attrs;
> > +};
>
> I know you all are off in the weeds designing some new crazy api for
> this instead of this current proposal (sorry, I lost the thread, I'll
> wait for the patches before commenting on it), but I do want to say one
> thing here.
>
> NEVER use a raw kobject as a child for a 'struct device' unless you
> REALLY REALLY REALLY REALLY know what you are doing and have a VERY good
> reason to do so.
>
> Just use a 'struct device', otherwise you end up having to reinvent all
> of the core logic that struct device provides you, like attribute
> callbacks (which you had to create), and other good stuff like telling
> userspace that a device has shown up so it knows to look at it.
>
> That last one is key, a kobject is suddenly a "black hole" in sysfs as
> far as userspace knows because it does not see them for the most part
> (unless you are mucking around in the filesystem on your own, and
> really, don't do that, use a library like the rest of the world unless
> you really like reinventing everything, which, from your patchset it
> feels like...)
>
> Anyway, use 'struct device'. That's all.
>
> greg k-h
Okay, thank you for the advice. I prefer to reuse over reinvent. :)
I only used kobject because the power/ directory was automatically
created with 'struct device', but I now I see there are better ways to
suppress that.
next prev parent reply other threads:[~2018-11-26 19:56 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 22:49 [PATCH 1/7] node: Link memory nodes to their compute nodes Keith Busch
2018-11-14 22:49 ` [PATCH 2/7] node: Add heterogenous memory performance Keith Busch
2018-11-19 3:35 ` Anshuman Khandual
2018-11-19 15:46 ` Keith Busch
2018-11-22 13:22 ` Anshuman Khandual
2018-11-27 7:00 ` Dan Williams
2018-11-27 17:42 ` Dan Williams
2018-11-27 17:44 ` Keith Busch
2018-11-14 22:49 ` [PATCH 3/7] doc/vm: New documentation for " Keith Busch
2018-11-15 12:59 ` Jonathan Cameron
2018-12-10 16:12 ` Dan Williams
2018-11-20 13:51 ` Mike Rapoport
2018-11-20 15:31 ` Keith Busch
2018-11-14 22:49 ` [PATCH 4/7] node: Add memory caching attributes Keith Busch
2018-11-15 0:40 ` Dave Hansen
2018-11-19 4:14 ` Anshuman Khandual
2018-11-19 23:06 ` Keith Busch
2018-11-22 13:29 ` Anshuman Khandual
2018-11-26 15:14 ` Keith Busch
2018-11-26 19:06 ` Greg Kroah-Hartman
2018-11-26 19:53 ` Keith Busch [this message]
2018-11-26 19:06 ` Greg Kroah-Hartman
2018-11-14 22:49 ` [PATCH 5/7] doc/vm: New documentation for memory cache Keith Busch
2018-11-15 0:41 ` Dave Hansen
2018-11-15 13:16 ` Jonathan Cameron
2018-11-20 13:53 ` Mike Rapoport
2018-11-14 22:49 ` [PATCH 6/7] acpi: Create subtable parsing infrastructure Keith Busch
2018-11-19 9:58 ` Rafael J. Wysocki
2018-11-19 18:36 ` Keith Busch
2018-11-14 22:49 ` [PATCH 7/7] acpi/hmat: Parse and report heterogeneous memory Keith Busch
2018-11-15 13:57 ` [PATCH 1/7] node: Link memory nodes to their compute nodes Matthew Wilcox
2018-11-15 14:59 ` Keith Busch
2018-11-15 17:50 ` Dan Williams
2018-11-19 3:04 ` Anshuman Khandual
2018-11-15 20:36 ` Matthew Wilcox
2018-11-16 18:32 ` Keith Busch
2018-11-19 3:15 ` Anshuman Khandual
2018-11-19 15:49 ` Keith Busch
2018-12-04 15:43 ` Aneesh Kumar K.V
2018-12-04 16:54 ` Keith Busch
2018-11-16 22:55 ` Dan Williams
2018-11-19 2:52 ` Anshuman Khandual
2018-11-19 2:46 ` Anshuman Khandual
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