On Thu, May 27, 2021 at 05:01:53PM -0700, Darrick J. Wong wrote: > On Thu, May 27, 2021 at 06:52:15PM +1000, Dave Chinner wrote: > > On Wed, May 26, 2021 at 11:19:47PM -0700, Darrick J. Wong wrote: > > > On Thu, May 27, 2021 at 02:52:02PM +1000, Dave Chinner wrote: > > > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > > > > > Ever since we moved to deferred freeing of extents, we only every > > > > free one extent per transaction. We separated the bulk unmapping of > > > > extents from the submission of EFI/free/EFD transactions, and hence > > > > while we unmap extents in bulk, we only every free one per > > > > transaction. > > > > > > > > Our transaction reservations still live in the era from before > > > > deferred freeing of extents, so still refer to "xfs_bmap_finish" > > > > and it needing to free multiple extents per transaction. These > > > > freeing reservations can now all be reduced to a single extent to > > > > reflect how we currently free extents. > > > > > > > > This significantly reduces the reservation sizes for operations like > > > > truncate and directory operations where they currently reserve space > > > > for freeing up to 4 extents per transaction. > > > > > > > > For a 4kB block size filesytsem with reflink=1,rmapbt=1, the > > > > reservation sizes change like this: > > > > > > > > Reservation Before After > > > > (index) logres logcount logres logcount > > > > 0 write 314104 8 314104 8 > > > > 1 itruncate 579456 8 148608 8 > > > > 2 rename 435840 2 307936 2 > > > > 3 link 191600 2 191600 2 > > > > 4 remove 312960 2 174328 2 > > > > 5 symlink 470656 3 470656 3 > > > > 6 create 469504 2 469504 2 > > > > 7 create_tmpfile 490240 2 490240 2 > > > > 8 mkdir 469504 3 469504 3 > > > > 9 ifree 508664 2 508664 2 > > > > 10 ichange 5752 0 5752 0 > > > > 11 growdata 147840 2 147840 2 > > > > 12 addafork 178936 2 178936 2 > > > > 13 writeid 760 0 760 0 > > > > 14 attrinval 578688 1 147840 1 > > > > 15 attrsetm 26872 3 26872 3 > > > > 16 attrsetrt 16896 0 16896 0 > > > > 17 attrrm 292224 3 148608 3 > > > > 18 clearagi 4224 0 4224 0 > > > > 19 growrtalloc 173944 2 173944 2 > > > > 20 growrtzero 4224 0 4224 0 > > > > 21 growrtfree 10096 0 10096 0 > > > > 22 qm_setqlim 232 1 232 1 > > > > 23 qm_dqalloc 318327 8 318327 8 > > > > 24 qm_quotaoff 4544 1 4544 1 > > > > 25 qm_equotaoff 320 1 320 1 > > > > 26 sb 4224 1 4224 1 > > > > 27 fsyncts 760 0 760 0 > > > > MAX 579456 8 318327 8 > > > > > > > > So we can see that many of the reservations have gone substantially > > > > down in size. itruncate, rename, remove, attrinval and attrrm are > > > > much smaller now. The maximum reservation size has gone from being > > > > attrinval at 579456*8 bytes to dqalloc at 318327*8 bytes. This is a > > > > substantial improvement for common operations. > > > > > > If you're going to play around with log reservations, can you have a > > > quick look at the branch I made to fix all the oversized reservations > > > that we make for rmap and reflink? > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=reflink-speedups > > > > > > That's what's next after deferred inode inactivation lands. > > > > They all look reasonable at a first pass. I'd need to do more than > > read the patches to say they are definitely correct, but they > > certainly don't seem unreasonable to me. I'd also have to run > > numbers like the table above so I can quantify the reductions, > > but nothing shouted "don't do this!" to me.... > > Reservations before and after for a sample 100G filesystem: .... > type -1 res 547200 count 8 type -1 res 327552 count 5 > > IOWs, a 63% reduction in the size of an itruncate reservations. Nice! Do you want to add the three reservation patches from this patchset to your branch? Because... > Note that the patchset also includes the necessary pieces to continue > formatting filesystems with the same minimum log size rules as before so > that you can format with a new xfsprogs and still be able to mount on an > older kernel. ... this will be needed for either of these reduction patchsets. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
