Hi Guillem, Here are some rough patches implementing Ted's suggestions:
Ted Ts'o wrote: > extract(a); > sync_file_range(fd.a, 0, 0, SYNC_FILE_RANGE_WRITE); > extract(b.dpkg-new); > sync_file_range(fd.b, 0, 0, SYNC_FILE_RANGE_WRITE); > extract(c.dpkg-new); > sync_file_range(fd.c, 0, 0, SYNC_FILE_RANGE_WRITE); > > sync_file_range(fd.a, 0, 0, SYNC_FILE_RANGE_WAIT_BEFORE); > sync_file_range(fd.b, 0, 0, SYNC_FILE_RANGE_WAIT_BEFORE); > sync_file_range(fd.c, 0, 0, SYNC_FILE_RANGE_WAIT_BEFORE); > > fdatasync(a); > fdatasync(b.dpkg-new); > fdatasync(c.dpkg-new); > > rename(b.dpkg-new, b); > rename(c.dpkg-new, c); Exceptions to what Ted did: this does not special-case new files and it intersperses fdatasync and rename. If that matters I'd be interested to learn that. Results (on ext4) suggest that patches 1 and 4 matter and the rest are within noise. Timings are rough; sometimes replicates vary by as much as a second. Numbers are cold cache (i.e., after running sync and echo 3>.../drop_caches), best of 3, dpkg --install python2.7 and python2.7-minimal. before: 5.73user 1.62system 0:33.84elapsed 21%CPU (0avgtext+0avgdata 89968maxresident)k 0inputs+0outputs (0major+46962minor)pagefaults 0swaps patch 1 (use SYNC_FILE_RANGE_WRITE): 5.64user 1.69system 0:10.47elapsed 69%CPU (0avgtext+0avgdata 90000maxresident)k 0inputs+0outputs (0major+46948minor)pagefaults 0swaps patch 1+2 (use SYNC_FILE_RANGE_WAIT_BEFORE): 5.48user 1.61system 0:10.43elapsed 70%CPU (0avgtext+0avgdata 90000maxresident)k 0inputs+0outputs (0major+46958minor)pagefaults 0swaps patch 1+2+3 (delay first fsync): 5.63user 1.66system 0:10.45elapsed 70%CPU (0avgtext+0avgdata 89984maxresident)k 0inputs+0outputs (0major+46966minor)pagefaults 0swaps patch 1+2+3+4 (use fdatasync): 5.65user 1.60system 0:10.24elapsed 71%CPU (0avgtext+0avgdata 90016maxresident)k 0inputs+0outputs (0major+46977minor)pagefaults 0swaps Jonathan Nieder (4): dpkg: On Linux initiate writeback of unpacked files ASAP dpkg: On Linux finish writeback before fsync dpkg: Write back all files before first fsync dpkg: Use fdatasync instead of fsync src/archives.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 49 insertions(+), 1 deletions(-) -- To UNSUBSCRIBE, email to debian-kernel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20101129064825.ga6...@burratino
