On Thursday, December 10, 2015 2:26:38 AM CEST Pádraig Brady wrote: > On 09/12/15 10:35, Pádraig Brady wrote: > > On 09/12/15 06:34, Kamil Dudka wrote: > >> The flag is needed to implement the -noleaf option of find. > >> * lib/fts.c (link_count_optimize_ok): Implement the FTS_NOLEAF flag. > >> * lib/fts_.h (FTS_NOLEAF): New macro, shifted conflicting constants. > > > > Is this exposed to fix issues with certain file systems, > > or just in case there may be issues, or support easily > > testing find without the leaf optimization? > > > > I see Jim said the current FTS implementation > > would make -noleaf a no-op there: > > https://lists.gnu.org/archive/html/bug-gnulib/2008-12/msg00280.html > > > > cheers, > > Pádraig. > > > > p.s. I see that find does a stat per file on XFS, > > while d_type can be used to distinguish dirs there. > > On XFS DT_DIR is set for dirs and DT_UNKNOWN otherwise. > > I wonder is there some optimization we could do for that case. > > I did a quick check on XFS which suggests the leaf optimization > based on st_nlink is valid: > test $(($(find . -maxdepth 1 -type d | wc -l) + 1)) = $(stat -c %h .) && > echo leaf_ok > > Applying this diff: > @@ -717,6 +718,7 @@ leaf_optimization_applies (int dir_fd) > { > /* List here the file system types that lack usable dirent.d_type > info, yet for which the optimization does apply. */ > + case S_MAGIC_XFS: > case S_MAGIC_REISERFS: > return true; > > Gives this significant speedup: > $ time find/find-before /usr/share >/dev/null > real 0m0.410s > user 0m0.145s > sys 0m0.266s > > $ time find/find-after /usr/share >/dev/null > real 0m0.278s > user 0m0.147s > sys 0m0.131s
Pádraig, do you remember which kernel you tested it with? I am currently not able to get any speedup on XFS with Fedora/el7 kernels... Kamil > I also noticed a lot of fcntl calls on XFS > (basically one per file), which I need to look further into: > $ strace -c find/find /usr/share >/dev/null > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 40.03 0.147809 1 151710 fcntl > 17.62 0.065069 1 63154 close > 14.52 0.053608 1 40071 newfstatat > 13.15 0.048547 1 35400 getdents > > cheers, > Pádraig
