From: Jeff Moyer <jmoyer@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>, Jan Kara <jack@suse.cz>,
Pankaj Gupta <pagupta@redhat.com>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
virtualization@lists.linux-foundation.org,
KVM list <kvm@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux ACPI <linux-acpi@vger.kernel.org>,
Qemu Developers <qemu-devel@nongnu.org>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>,
Ross Zwisler <zwisler@kernel.org>,
Vishal L Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>, "Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
lcapitulino@redhat.com, Kevin Wolf <kwolf@redhat.com>,
Igor Mammedov <imammedo@redhat.com>,
Nitesh Narayan Lal <nilal@redhat.com>,
Rik van Riel <riel@surriel.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
David Hildenbrand <david@redhat.com>, david <david@fromorbit.com>,
cohuck@redhat.com, Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kilobyte@angband.pl, yuval shaia <yuval.shaia@oracle.com>
Subject: Re: [PATCH v5 1/6] libnvdimm: nd_region flush callback support
Date: Mon, 22 Apr 2019 11:51:35 -0400 [thread overview]
Message-ID: <x497ebm82d4.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <CAPcyv4jPOF_+R6U17J_+88+X8LC-LSPCugA6gbKxuphuuFB2gg@mail.gmail.com> (Dan Williams's message of "Thu, 18 Apr 2019 11:14:59 -0700")
Dan Williams <dan.j.williams@intel.com> writes:
> On Thu, Apr 18, 2019 at 9:18 AM Christoph Hellwig <hch@infradead.org> wrote:
>>
>> On Thu, Apr 18, 2019 at 09:05:05AM -0700, Dan Williams wrote:
>> > > > I'd either add a comment about avoiding retpoline overhead here or just
>> > > > make ->flush == NULL mean generic_nvdimm_flush(). Just so that people don't
>> > > > get confused by the code.
>> > >
>> > > Isn't this premature optimization? I really don't like adding things
>> > > like this without some numbers to show it's worth it.
>> >
>> > I don't think it's premature given this optimization technique is
>> > already being deployed elsewhere, see:
>> >
>> > https://lwn.net/Articles/774347/
>>
>> For one this one was backed by numbers, and second after feedback
>> from Linux we switched to the NULL pointer check instead.
>
> Ok I should have noticed the switch to NULL pointer check. However,
> the question still stands do we want everyone to run numbers to
> justify this optimization, or make it a new common kernel coding
> practice to do:
>
> if (!object->op)
> generic_op(object);
> else
> object->op(object);
>
> ...in hot paths?
I don't think nvdimm_flush is a hot path. Numbers of some
representative workload would prove one of us right.
-Jeff
next prev parent reply other threads:[~2019-04-22 15:51 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 4:08 [PATCH v5 0/6] virtio pmem driver Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 1/6] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-04-11 14:51 ` Dan Williams
2019-04-11 15:57 ` [Qemu-devel] " Pankaj Gupta
2019-04-11 16:09 ` Dan Williams
2019-04-11 16:23 ` Pankaj Gupta
2019-04-12 8:32 ` Jan Kara
2019-04-12 13:12 ` Jeff Moyer
2019-04-18 6:27 ` [Qemu-devel] " Pankaj Gupta
2019-04-18 16:05 ` Dan Williams
2019-04-18 16:10 ` Jeff Moyer
2019-04-18 16:18 ` Christoph Hellwig
2019-04-18 18:14 ` Dan Williams
2019-04-22 15:51 ` Jeff Moyer [this message]
2019-04-22 19:44 ` Dan Williams
2019-04-22 21:03 ` Jeff Moyer
2019-04-23 4:07 ` Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 2/5] virtio-pmem: Add virtio pmem driver Pankaj Gupta
2019-04-10 12:24 ` Cornelia Huck
2019-04-10 14:38 ` Yuval Shaia
2019-04-10 15:44 ` Pankaj Gupta
2019-04-10 15:38 ` Pankaj Gupta
2019-04-10 13:12 ` Michael S. Tsirkin
2019-04-10 14:03 ` [Qemu-devel] " Pankaj Gupta
2019-04-10 14:31 ` Cornelia Huck
2019-04-10 16:46 ` Michael S. Tsirkin
2019-04-10 16:52 ` Cornelia Huck
2019-04-10 14:41 ` Yuval Shaia
2019-04-10 4:08 ` [PATCH v5 3/6] libnvdimm: add dax_dev sync flag Pankaj Gupta
2019-04-10 8:28 ` Jan Kara
2019-04-10 8:38 ` Pankaj Gupta
2019-04-11 14:56 ` Dan Williams
2019-04-11 15:39 ` Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 4/6] dax: check synchronous mapping is supported Pankaj Gupta
2019-04-10 8:25 ` Jan Kara
2019-04-10 8:31 ` Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 5/6] ext4: disable map_sync for async flush Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 6/6] xfs: " Pankaj Gupta
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=x497ebm82d4.fsf@segfault.boston.devel.redhat.com \
--to=jmoyer@redhat.com \
--cc=aarcange@redhat.com \
--cc=adilger.kernel@dilger.ca \
--cc=cohuck@redhat.com \
--cc=dan.j.williams@intel.com \
--cc=darrick.wong@oracle.com \
--cc=dave.jiang@intel.com \
--cc=david@fromorbit.com \
--cc=david@redhat.com \
--cc=hch@infradead.org \
--cc=imammedo@redhat.com \
--cc=jack@suse.cz \
--cc=jasowang@redhat.com \
--cc=kilobyte@angband.pl \
--cc=kvm@vger.kernel.org \
--cc=kwolf@redhat.com \
--cc=lcapitulino@redhat.com \
--cc=lenb@kernel.org \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=linux-xfs@vger.kernel.org \
--cc=mst@redhat.com \
--cc=nilal@redhat.com \
--cc=pagupta@redhat.com \
--cc=pbonzini@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=riel@surriel.com \
--cc=rjw@rjwysocki.net \
--cc=stefanha@redhat.com \
--cc=tytso@mit.edu \
--cc=virtualization@lists.linux-foundation.org \
--cc=vishal.l.verma@intel.com \
--cc=willy@infradead.org \
--cc=xiaoguangrong.eric@gmail.com \
--cc=yuval.shaia@oracle.com \
--cc=zwisler@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 NNTP newsgroup(s).