From: Chaitanya Kulkarni <chaitanyak@nvidia.com>
To: "ira.weiny@intel.com" <ira.weiny@intel.com>,
Andy Whitcroft <apw@canonical.com>, Joe Perches <joe@perches.com>
Cc: "nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-sh@vger.kernel.org" <linux-sh@vger.kernel.org>,
"kgdb-bugreport@lists.sourceforge.net"
<kgdb-bugreport@lists.sourceforge.net>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
"linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
"dm-devel@redhat.com" <dm-devel@redhat.com>,
"keyrings@vger.kernel.org" <keyrings@vger.kernel.org>,
"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
"sparclinux@vger.kernel.org" <sparclinux@vger.kernel.org>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"linux1394-devel@lists.sourceforge.net"
<linux1394-devel@lists.sourceforge.net>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"linux-csky@vger.kernel.org" <linux-csky@vger.kernel.org>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"linux-snps-arc@lists.infradead.org"
<linux-snps-arc@lists.infradead.org>,
"Fabio M . De Francesco" <fmdefrancesco@gmail.com>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
"linux-xtensa@linux-xtensa.org" <linux-xtensa@linux-xtensa.org>,
"linux-um@lists.infradead.org" <linux-um@lists.infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
"loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
Thomas Gleixner <tglx@linutronix.de>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] checkpatch: Add kmap and kmap_atomic to the deprecated list
Date: Sun, 14 Aug 2022 05:25:30 +0000 [thread overview]
Message-ID: <91f708ed-f456-dc83-281e-fc18a0b4b981@nvidia.com> (raw)
In-Reply-To: <20220813220034.806698-1-ira.weiny@intel.com>
On 8/13/22 15:00, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> kmap() and kmap_atomic() are being deprecated in favor of
> kmap_local_page().
>
> There are two main problems with kmap(): (1) It comes with an overhead
> as mapping space is restricted and protected by a global lock for
> synchronization and (2) it also requires global TLB invalidation when
> the kmap’s pool wraps and it might block when the mapping space is fully
> utilized until a slot becomes available.
>
> kmap_local_page() is safe from any context and is therefore redundant
> with kmap_atomic() with the exception of any pagefault or preemption
> disable requirements. However, using kmap_atomic() for these side
> effects makes the code less clear. So any requirement for pagefault or
> preemption disable should be made explicitly.
>
> With kmap_local_page() the mappings are per thread, CPU local, can take
> page faults, and can be called from any context (including interrupts).
> It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore,
> the tasks can be preempted and, when they are scheduled to run again,
> the kernel virtual addresses are restored.
>
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
> ---
> Suggested by credits.
> Thomas: Idea to keep from growing more kmap/kmap_atomic calls.
> Fabio: Stole some of his boiler plate commit message.
>
> Notes on tree-wide conversions:
>
> I've cc'ed mailing lists for subsystems which currently contains either kmap()
> or kmap_atomic() calls. As some of you already know Fabio and I have been
> working through converting kmap() calls to kmap_local_page(). But there is a
> lot more work to be done. Help from the community is always welcome,
> especially with kmap_atomic() conversions. To keep from stepping on each
> others toes I've created a spreadsheet of the current calls[1]. Please let me
> or Fabio know if you plan on tacking one of the conversions so we can mark it
> off the list.
>
> [1] https://docs.google.com/spreadsheets/d/1i_ckZ10p90bH_CkxD2bYNi05S2Qz84E2OFPv8zq__0w/edit#gid=1679714357
>
Looks good.
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
prev parent reply other threads:[~2022-08-14 5:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-13 22:00 [PATCH] checkpatch: Add kmap and kmap_atomic to the deprecated list ira.weiny
2022-08-14 5:25 ` Chaitanya Kulkarni [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=91f708ed-f456-dc83-281e-fc18a0b4b981@nvidia.com \
--to=chaitanyak@nvidia.com \
--cc=akpm@linux-foundation.org \
--cc=apw@canonical.com \
--cc=bpf@vger.kernel.org \
--cc=dm-devel@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=fmdefrancesco@gmail.com \
--cc=iommu@lists.linux.dev \
--cc=ira.weiny@intel.com \
--cc=joe@perches.com \
--cc=keyrings@vger.kernel.org \
--cc=kgdb-bugreport@lists.sourceforge.net \
--cc=kvm@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-csky@vger.kernel.org \
--cc=linux-edac@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-ide@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-mmc@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=linux-nvme@lists.infradead.org \
--cc=linux-raid@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=linux-scsi@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=linux-snps-arc@lists.infradead.org \
--cc=linux-um@lists.infradead.org \
--cc=linux-xtensa@linux-xtensa.org \
--cc=linux1394-devel@lists.sourceforge.net \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=loongarch@lists.linux.dev \
--cc=netdev@vger.kernel.org \
--cc=nvdimm@lists.linux.dev \
--cc=sparclinux@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=virtualization@lists.linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).