From: Christoph Hellwig <hch@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jeff Moyer <jmoyer@redhat.com>, 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>,
Christoph
Subject: Re: [PATCH v5 1/6] libnvdimm: nd_region flush callback support
Date: Thu, 18 Apr 2019 09:18:34 -0700 [thread overview]
Message-ID: <20190418161833.GA22970@infradead.org> (raw)
In-Reply-To: <CAPcyv4jrNHqW3FuGkeo==ZoJr7LKahCv4_esnokfy7enek8=2Q@mail.gmail.com>
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.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jeff Moyer <jmoyer@redhat.com>, 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>,
Christoph Hellwig <hch@infradead.org>,
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: Thu, 18 Apr 2019 09:18:34 -0700 [thread overview]
Message-ID: <20190418161833.GA22970@infradead.org> (raw)
Message-ID: <20190418161834.vratXYnH7hLBqEoXf2meJRTT9QKQ-D1zDqTOYC3uaDw@z> (raw)
In-Reply-To: <CAPcyv4jrNHqW3FuGkeo==ZoJr7LKahCv4_esnokfy7enek8=2Q@mail.gmail.com>
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.
next prev parent reply other threads:[~2019-04-18 16:18 UTC|newest]
Thread overview: 77+ 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 ` Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 3/6] libnvdimm: add dax_dev sync flag Pankaj Gupta
2019-04-10 4:08 ` Pankaj Gupta
2019-04-10 8:28 ` Jan Kara
2019-04-10 8:28 ` Jan Kara
2019-04-10 8:38 ` Pankaj Gupta
2019-04-10 8:38 ` Pankaj Gupta
2019-04-11 14:56 ` Dan Williams
2019-04-11 14:56 ` Dan Williams
2019-04-11 15:39 ` Pankaj Gupta
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 4:08 ` Pankaj Gupta
[not found] ` <20190410040826.24371-5-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-04-10 8:25 ` Jan Kara
2019-04-10 8:25 ` Jan Kara
2019-04-10 8:31 ` Pankaj Gupta
2019-04-10 8:31 ` Pankaj Gupta
[not found] ` <20190410040826.24371-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-04-10 4:08 ` [PATCH v5 1/6] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-04-10 4:08 ` Pankaj Gupta
[not found] ` <20190410040826.24371-2-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-04-11 14:51 ` Dan Williams
2019-04-11 14:51 ` Dan Williams
2019-04-11 15:57 ` [Qemu-devel] " Pankaj Gupta
2019-04-11 15:57 ` Pankaj Gupta
[not found] ` <1463291806.21158433.1554998258746.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-04-11 16:09 ` Dan Williams
2019-04-11 16:09 ` Dan Williams
2019-04-11 16:23 ` Pankaj Gupta
2019-04-11 16:23 ` Pankaj Gupta
2019-04-12 8:32 ` Jan Kara
2019-04-12 8:32 ` Jan Kara
2019-04-12 13:12 ` Jeff Moyer
2019-04-12 13:12 ` Jeff Moyer
2019-04-18 6:27 ` [Qemu-devel] " Pankaj Gupta
2019-04-18 6:27 ` Pankaj Gupta
2019-04-18 16:05 ` Dan Williams
2019-04-18 16:05 ` Dan Williams
2019-04-18 16:10 ` Jeff Moyer
2019-04-18 16:10 ` Jeff Moyer
2019-04-18 16:18 ` Christoph Hellwig [this message]
2019-04-18 16:18 ` Christoph Hellwig
[not found] ` <20190418161833.GA22970-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2019-04-18 18:14 ` Dan Williams
2019-04-18 18:14 ` Dan Williams
2019-04-22 15:51 ` Jeff Moyer
2019-04-22 15:51 ` Jeff Moyer
2019-04-22 19:44 ` Dan Williams
2019-04-22 19:44 ` Dan Williams
2019-04-22 21:03 ` Jeff Moyer
2019-04-22 21:03 ` Jeff Moyer
[not found] ` <x49ef5t7nwp.fsf-RRHT56Q3PSP4kTEheFKJxxDDeQx5vsVwAInAS/Ez/D0@public.gmane.org>
2019-04-23 4:07 ` Pankaj Gupta
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 4:08 ` Pankaj Gupta
2019-04-10 12:24 ` Cornelia Huck
2019-04-10 12:24 ` Cornelia Huck
[not found] ` <20190410142426.5bf0d9a4.cohuck-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-04-10 14:38 ` Yuval Shaia
2019-04-10 14:38 ` Yuval Shaia
2019-04-10 15:44 ` Pankaj Gupta
2019-04-10 15:44 ` Pankaj Gupta
2019-04-10 15:38 ` Pankaj Gupta
2019-04-10 15:38 ` Pankaj Gupta
[not found] ` <20190410040826.24371-3-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-04-10 13:12 ` Michael S. Tsirkin
2019-04-10 13:12 ` Michael S. Tsirkin
[not found] ` <20190410091216-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2019-04-10 14:03 ` [Qemu-devel] " Pankaj Gupta
2019-04-10 14:03 ` Pankaj Gupta
2019-04-10 14:31 ` Cornelia Huck
2019-04-10 14:31 ` Cornelia Huck
2019-04-10 16:46 ` Michael S. Tsirkin
2019-04-10 16:46 ` Michael S. Tsirkin
2019-04-10 16:52 ` Cornelia Huck
2019-04-10 16:52 ` Cornelia Huck
2019-04-10 14:41 ` Yuval Shaia
2019-04-10 14:41 ` Yuval Shaia
2019-04-10 4:08 ` [PATCH v5 5/6] ext4: disable map_sync for async flush Pankaj Gupta
2019-04-10 4:08 ` Pankaj Gupta
2019-04-10 4:08 ` [PATCH v5 6/6] xfs: " Pankaj Gupta
2019-04-10 4:08 ` Pankaj Gupta
2019-04-10 8:08 ` [PATCH v5 0/6] virtio pmem driver Arkadiusz Miśkiewicz
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