From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Layton Subject: Re: [PATCH 86/87] fs: switch timespec64 fields in inode to discrete integers Date: Thu, 28 Sep 2023 13:06:03 -0400 Message-ID: References: <20230928110554.34758-1-jlayton@kernel.org> <20230928110554.34758-2-jlayton@kernel.org> <6020d6e7-b187-4abb-bf38-dc09d8bd0f6d@app.fastmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695920779; bh=DNM/VlOuUT51G0bnMvXw+94sqfHee3c68K5vLwQuau4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=T1EG9wCsmdavqbCDgZQmRYDY2hTjqQ8HvqU7HakqZRoba0+m8x7Xb0PPxNH54fTbK gxOvKBrhR/NUHAqOFYLgQFvCS4fbqqpdpyJ0meCz+VJBZB5WwUDXaofxixCnDwGA2b xVhvTR3lvjwhcUNCr4cL+zM4prum42dBj/EqssN3wQ5xwZohTtnO5wenm4djJ5rTsg au+O/I2DWLjGqSGQ9+pJFDrXNkgJ5uSZlH8zfxoOHymWjEqjSumVZbYplcXqZfm3+f KDfZ0aAr31be94G8szYCClaMWLFdZEYGpG76Y3w4tHoT3E7mgxWznMj5HFQTi8O+xa SaKUjb/2UX2Ww== In-Reply-To: <6020d6e7-b187-4abb-bf38-dc09d8bd0f6d@app.fastmail.com> List-ID: Content-Type: text/plain; charset="us-ascii" To: Arnd Bergmann , Alexander Viro , Christian Brauner , Linus Torvalds , David Sterba , Amir Goldstein , Theodore Ts'o , "Eric W. Biederman" , Kees Cook , Jeremy Kerr , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Greg Kroah-Hartman , Arve Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-rdma@vger.kernel.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, autofs@vger.kernel.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, codalist@coda.cs.cmu.edu, linux-efi@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, gfs2@lists.linux.dev, linux-um@lists.infradead.org, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, linux-nfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, ntfs3@lists.linux.dev, ocfs2-d On Thu, 2023-09-28 at 11:48 -0400, Arnd Bergmann wrote: > On Thu, Sep 28, 2023, at 07:05, Jeff Layton wrote: > > This shaves 8 bytes off struct inode, according to pahole. > >=20 > > Signed-off-by: Jeff Layton >=20 > FWIW, this is similar to the approach that Deepa suggested > back in 2016: >=20 > https://lore.kernel.org/lkml/1452144972-15802-3-git-send-email-deepa.kern= el@gmail.com/ >=20 > It was NaKed at the time because of the added complexity, > though it would have been much easier to do it then, > as we had to touch all the timespec references anyway. >=20 > The approach still seems ok to me, but I'm not sure it's worth > doing it now if we didn't do it then. >=20 I remember seeing those patches go by. I don't remember that change being NaK'ed, but I wasn't paying close attention at the time=20 Looking at it objectively now, I think it's worth it to recover 8 bytes per inode and open a 4 byte hole that Amir can use to grow the i_fsnotify_mask. We might even able to shave off another 12 bytes eventually if we can move to a single 64-bit word per timestamp.=20 It is a lot of churn though. --=20 Jeff Layton