Date: Thu, 13 Dec 2012 01:50:52 +1100 (EST) From: Bruce Evans <brde@optusnet.com.au> To: =?ISO-8859-1?Q?Olav_Gr=F8n=E5s_Gjerde?= <olavgg@gmail.com> Cc: freebsd-fs@freebsd.org, freebsd-performance@freebsd.org Subject: Re: find vs ls performance for walking folders, are there any faster options? Message-ID: <20121213012632.M1201@besplex.bde.org> In-Reply-To: <CALL7tK9uRz2qLDqHKOqKLrM7oPc4UvYj0s6zxh6VNFQLYoyPTQ@mail.gmail.com> References: <CALL7tK9uRz2qLDqHKOqKLrM7oPc4UvYj0s6zxh6VNFQLYoyPTQ@mail.gmail.com>
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This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --0-821341582-1355323852=:1201 Content-Type: TEXT/PLAIN; charset=X-UNKNOWN; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE On Wed, 12 Dec 2012, [ISO-8859-1] Olav Gr=F8n=E5s Gjerde wrote: > I'm working on scanning filesystems to build a file search engine and > came over something interesting. > > I can walk through 300 000 folders in ~19.5seconds with this command: > ls -Ra | grep -e "./.*:" | sed "s/://" > > With find, it surprisingly takes ~50.5 seconds.: > find . -type d This is because 'find' with '-type' lstats all the files. It doesn't use DT_DIR from dirent for some reason. ls can be slowed down similarly using -F. > My results are based on five runs of each command to warm up the disk cac= he. > I've tried both this with both UFS and ZFS, and both filesystems shows > the same speed difference. I get almost exactly the same ratio of speeds on an old version of FreeBSD. All the data was cached, and there were only 7 symlinks. Thr file system was mounted with -noatime, so the cache actually worked. > On a modern Linux distribution(Ubuntu 12.10 with EXT4), ls is just > slight faster than find(about 15-20%). Apparently lstat() is relatively much slower in FreeBSD. It only takes 5 usec here, but that is a lot for converting cached data (getpid() takes 0.2 usec). A file system mounted with -atime might be much slower, for writing directory timestamps (the sync of the timestamps is delayed, but it is a very heavyweight operation). > Are there a faster way to walk folders on FreeBSD? Are there some > options(sysctl) I could tune to improve the performance? Nothing much faster than find without -type. Whatever fts(3) gives. Bruce --0-821341582-1355323852=:1201--
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