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Wong" To: Andiry Xu Cc: "Theodore Y. Ts'o" , Arnd Bergmann , Linux FS Devel , Linux Kernel Mailing List , "linux-nvdimm@lists.01.org" , Dan Williams , "Rudoff, Andy" , coughlan@redhat.com, Steven Swanson , Dave Chinner , Jan Kara , swhiteho@redhat.com, miklos@szeredi.hu, Jian Xu , Andiry Xu Subject: Re: [RFC v2 03/83] Add super.h. Message-ID: <20180316063045.GI4875@magnolia> References: <1520705944-6723-1-git-send-email-jix024@eng.ucsd.edu> <1520705944-6723-4-git-send-email-jix024@eng.ucsd.edu> <20180315045401.GB4860@magnolia> <20180316025928.GB2254@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8833 signatures=668690 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=891 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1803160005 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2018 at 11:17:54PM -0700, Andiry Xu wrote: > On Thu, Mar 15, 2018 at 7:59 PM, Theodore Y. Ts'o wrote: > > On Thu, Mar 15, 2018 at 09:38:29PM +0100, Arnd Bergmann wrote: > >> > >> You could also have a resolution of less than a nanosecond. Note > >> that today, the file time stamps generated by the kernel are in > >> jiffies resolution, so at best one millisecond. However, most modern > >> file systems go with the 64+32 bit timestamps because it's not all > >> that expensive. > > > > It actually depends on the architecture and the accuracy/granularity > > of the timekeeping hardware available to the system, but it's possible > > for the granularity of file time stamps to be up to one nanosecond. > > So you can get results like this: > > > > % stat unix_io.o > > File: unix_io.o > > Size: 55000 Blocks: 112 IO Block: 4096 regular file > > Device: fc01h/64513d Inode: 19931278 Links: 1 > > Access: (0644/-rw-r--r--) Uid: (15806/ tytso) Gid: (15806/ tytso) > > Access: 2018-03-15 18:09:21.679914182 -0400 > > Modify: 2018-03-15 18:09:21.639914089 -0400 > > Change: 2018-03-15 18:09:21.639914089 -0400 > > > > Thanks for all the suggestions. I think I will follow ext4's time > format. 2446 should be far away enough. If you do, try to avoid the encoding problems that ext4 (still) has: Not-fixed-by: a4dad1ae24f8 ("ext4: Fix handling of extended tv_sec") --D > Thanks, > Andiry