From: Yanmin Zhang <yanmin_zhang@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
dave@sr71.net
Cc: dan.j.williams@intel.com, dave.jiang@intel.com,
zwisler@kernel.org, vishal.l.verma@intel.com,
thomas.lendacky@amd.com, akpm@linux-foundation.org,
mhocko@suse.com, linux-nvdimm@lists.01.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
ying.huang@intel.com, fengguang.wu@intel.com, bp@suse.de,
bhelgaas@google.com, baiyaowei@cmss.chinamobile.com,
tiwai@suse.de
Subject: Re: [PATCH 4/4] dax: "Hotplug" persistent memory for use like normal RAM
Date: Fri, 18 Jan 2019 15:47:32 +0800 [thread overview]
Message-ID: <74c01a55-1a47-d649-a32a-ea597c24ab4a@linux.intel.com> (raw)
In-Reply-To: <1e9377c6-11a0-3bbd-763d-d9347bd556cf@intel.com>
On 2019/1/17 下午11:17, Dave Hansen wrote:
> On 1/17/19 12:19 AM, Yanmin Zhang wrote:
>>>
>> I didn't try pmem and I am wondering it's slower than DRAM.
>> Should a flag, such like _GFP_PMEM, be added to distinguish it from
>> DRAM?
>
> Absolutely not. :)
Agree.
>
> We already have performance-differentiated memory, and lots of ways to
> enumerate and select it in the kernel (all of our NUMA infrastructure).
Kernel does manage memory like what you say.
My question is: with your patch, PMEM becomes normal RAM, then there is
a chance for kernel to allocate PMEM as DMA buffer.
Some super speed devices like 10Giga NIC, USB (SSIC connecting modem),
might not work well if DMA buffer is in PMEM as it's slower than DRAM.
Should your patchset consider it?
>
> PMEM is also just the first of many "kinds" of memory that folks want to
> build in systems and use a "RAM". We literally don't have space to put
> a flag in for each type.
>
>
next prev parent reply other threads:[~2019-01-18 7:47 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 18:18 [PATCH 0/4] Allow persistent memory to be used " Dave Hansen
2019-01-16 18:18 ` Dave Hansen
2019-01-16 18:19 ` [PATCH 1/4] mm/resource: return real error codes from walk failures Dave Hansen
2019-01-16 18:19 ` Dave Hansen
2019-01-16 20:38 ` Bjorn Helgaas
2019-01-16 20:38 ` Bjorn Helgaas
2019-01-16 18:19 ` [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children Dave Hansen
2019-01-16 18:19 ` Dave Hansen
2019-01-16 19:16 ` Jerome Glisse
2019-01-16 23:01 ` Dave Hansen
2019-01-16 23:38 ` Jerome Glisse
2019-01-23 20:03 ` Dave Hansen
2019-01-23 20:15 ` Jerome Glisse
2019-01-18 19:58 ` Dave Hansen
2019-01-18 20:26 ` Jerome Glisse
2019-01-23 17:05 ` Michal Hocko
2019-01-16 18:19 ` [PATCH 3/4] dax/kmem: let walk_system_ram_range() search child resources Dave Hansen
2019-01-16 18:19 ` Dave Hansen
2019-01-16 18:19 ` [PATCH 4/4] dax: "Hotplug" persistent memory for use like normal RAM Dave Hansen
2019-01-16 18:19 ` Dave Hansen
2019-01-16 21:16 ` Bjorn Helgaas
2019-01-16 21:16 ` Bjorn Helgaas
2019-01-16 21:40 ` Dave Hansen
2019-01-16 21:44 ` Bjorn Helgaas
2019-01-16 21:44 ` Bjorn Helgaas
2019-01-16 22:06 ` Dan Williams
2019-01-16 22:06 ` Dan Williams
2019-01-16 21:53 ` Dave Hansen
2019-01-16 21:59 ` Bjorn Helgaas
2019-01-16 21:59 ` Bjorn Helgaas
2019-01-16 21:31 ` Dan Williams
2019-01-16 21:31 ` Dan Williams
2019-01-17 5:21 ` Du, Fan
2019-01-17 16:56 ` Dan Williams
2019-01-17 16:56 ` Dan Williams
2019-01-17 8:19 ` Yanmin Zhang
2019-01-17 15:17 ` Dave Hansen
2019-01-18 7:47 ` Yanmin Zhang [this message]
2019-01-18 15:20 ` Dave Hansen
2019-01-17 16:29 ` [PATCH 0/4] Allow persistent memory to be used " Jeff Moyer
2019-01-17 16:29 ` Jeff Moyer
2019-01-17 16:47 ` Keith Busch
2019-01-17 17:20 ` Jeff Moyer
2019-01-17 17:20 ` Jeff Moyer
2019-01-17 19:34 ` Keith Busch
2019-01-17 21:57 ` Jeff Moyer
2019-01-17 21:57 ` Jeff Moyer
2019-01-18 11:48 ` Fengguang Wu
2019-01-17 16:50 ` Dan Williams
2019-01-17 16:50 ` Dan Williams
2019-01-17 22:43 ` Dave Hansen
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