From: Mateusz Guzik <mjguzik@gmail.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Christian Brauner <brauner@kernel.org>,
Dave Chinner <dchinner@redhat.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-bcachefs@vger.kernel.org,
Kent Overstreet <kent.overstreet@linux.dev>,
Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: (subset) [PATCH 22/32] vfs: inode cache conversion to hash-bl
Date: Sat, 21 Oct 2023 14:13:52 +0200 [thread overview]
Message-ID: <CAGudoHFcz1wQgQ53sy-HPJvJhx_DHhXcVVg3FfrFKHHdxt=scg@mail.gmail.com> (raw)
In-Reply-To: <CAGudoHHqpk+1b6KqeFr6ptnm-578A_72Ng3H848WZP0GoyUQbw@mail.gmail.com>
It was bugging me that find_inode_fast is at the top of the profile
(modulo the locking routine).
Internals don't look too bad (it skips collisions without taking
locks), so I started wondering if hashing is any good.
I re-ran the scan of 20 mln and started counting visited inodes for
each call, got this:
[0, 1) 58266 | |
[1, 2) 385228 |@@@ |
[2, 3) 1252480 |@@@@@@@@@@ |
[3, 4) 2710082 |@@@@@@@@@@@@@@@@@@@@@@@ |
[4, 5) 4385945 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[5, 6) 5662628 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[6, 7) 6074390 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[7, 8) 5575381 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[8, 9) 4475706 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[9, 10) 3183676 |@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[10, 11) 2041743 |@@@@@@@@@@@@@@@@@ |
[11, 12) 1189850 |@@@@@@@@@@ |
[12, 13) 637683 |@@@@@ |
[13, 14) 313830 |@@ |
[14, 15) 143277 |@ |
[15, 16) 61501 | |
[16, 17) 25116 | |
[17, 18) 9693 | |
[18, 19) 3435 | |
[19, 20) 1120 | |
[20, 21) 385 | |
[21, 22) 99 | |
[22, 23) 45 | |
[23, 24) 15 | |
[24, 25) 2 | |
[25, 26) 2 | |
[26, 27) 2 | |
I compared this to literally just taking the ino & i_hash_mask as the
value, got this:
[0, 1) 119800 | |
[1, 2) 508063 |@@@ |
[2, 3) 1576390 |@@@@@@@@@@@ |
[3, 4) 2763163 |@@@@@@@@@@@@@@@@@@@ |
[4, 5) 3696348 |@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[5, 6) 5975274 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[6, 7) 7253615 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[7, 8) 6563736 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[8, 9) 5012728 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ |
[9, 10) 3495208 |@@@@@@@@@@@@@@@@@@@@@@@@@ |
[10, 11) 1606659 |@@@@@@@@@@@ |
[11, 12) 459458 |@@@ |
[12, 13) 3940 | |
[13, 14) 21 | |
[14, 15) 6 | |
[15, 16) 2 | |
That is to say distribution is much better, in particular the longest
streak is 15 (as opposed to 26).
While I'm not saying just taking ino is any good, I am saying there is
room for improvement here as far as one mount point is concerned.
Side note is that sb could have a randomly generated seed instead of
its address, which should help distributing this better.
So tl;dr hash distribution leaves some room for improvement and
*maybe* I'll prod it some time next month. One can also grow the table
of course, but that's for later.
--
Mateusz Guzik <mjguzik gmail.com>
next prev parent reply other threads:[~2023-10-21 12:13 UTC|newest]
Thread overview: 186+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-09 16:56 [PATCH 00/32] bcachefs - a new COW filesystem Kent Overstreet
2023-05-09 16:56 ` [PATCH 01/32] Compiler Attributes: add __flatten Kent Overstreet
2023-05-09 17:04 ` Miguel Ojeda
2023-05-09 17:24 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 02/32] locking/lockdep: lock_class_is_held() Kent Overstreet
2023-05-09 19:30 ` Peter Zijlstra
2023-05-09 20:11 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 03/32] locking/lockdep: lockdep_set_no_check_recursion() Kent Overstreet
2023-05-09 19:31 ` Peter Zijlstra
2023-05-09 19:57 ` Kent Overstreet
2023-05-09 20:18 ` Kent Overstreet
2023-05-09 20:27 ` Waiman Long
2023-05-09 20:35 ` Kent Overstreet
2023-05-09 21:37 ` Waiman Long
2023-05-10 8:59 ` Peter Zijlstra
2023-05-10 20:38 ` Kent Overstreet
2023-05-11 8:25 ` Peter Zijlstra
2023-05-11 9:32 ` Kent Overstreet
2023-05-12 20:49 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 04/32] locking: SIX locks (shared/intent/exclusive) Kent Overstreet
2023-05-11 12:14 ` Jan Engelhardt
2023-05-12 20:58 ` Kent Overstreet
2023-05-12 22:39 ` Jan Engelhardt
2023-05-12 23:26 ` Kent Overstreet
2023-05-12 23:49 ` Randy Dunlap
2023-05-13 0:17 ` Kent Overstreet
2023-05-13 0:45 ` Eric Biggers
2023-05-13 0:51 ` Kent Overstreet
2023-05-14 12:15 ` Jeff Layton
2023-05-15 2:39 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 05/32] MAINTAINERS: Add entry for six locks Kent Overstreet
2023-05-09 16:56 ` [PATCH 06/32] sched: Add task_struct->faults_disabled_mapping Kent Overstreet
2023-05-10 1:07 ` Jan Kara
2023-05-10 6:18 ` Kent Overstreet
2023-05-23 13:34 ` Jan Kara
2023-05-23 16:21 ` [Cluster-devel] " Christoph Hellwig
2023-05-23 16:35 ` Kent Overstreet
2023-05-24 6:43 ` Christoph Hellwig
2023-05-24 8:09 ` Kent Overstreet
2023-05-25 8:58 ` Christoph Hellwig
2023-05-25 20:50 ` Kent Overstreet
2023-05-26 8:06 ` Christoph Hellwig
2023-05-26 8:34 ` Kent Overstreet
2023-05-25 21:40 ` Kent Overstreet
2023-05-25 22:25 ` Andreas Grünbacher
2023-05-25 23:20 ` Kent Overstreet
2023-05-26 0:05 ` Andreas Grünbacher
2023-05-26 0:39 ` Kent Overstreet
2023-05-26 8:10 ` Christoph Hellwig
2023-05-26 8:38 ` Kent Overstreet
2023-05-23 16:49 ` Kent Overstreet
2023-05-25 8:47 ` Jan Kara
2023-05-25 21:36 ` Kent Overstreet
2023-05-25 22:45 ` Andreas Grünbacher
2023-05-25 22:04 ` Andreas Grünbacher
2023-05-09 16:56 ` [PATCH 07/32] mm: Bring back vmalloc_exec Kent Overstreet
2023-05-09 18:19 ` Lorenzo Stoakes
2023-05-09 20:15 ` Kent Overstreet
2023-05-09 20:46 ` Christoph Hellwig
2023-05-09 21:12 ` Lorenzo Stoakes
2023-05-09 21:29 ` Kent Overstreet
2023-05-10 6:48 ` Eric Biggers
2023-05-12 18:36 ` Kent Overstreet
2023-05-13 1:57 ` Eric Biggers
2023-05-13 19:28 ` Kent Overstreet
2023-05-14 5:45 ` Kent Overstreet
2023-05-14 18:43 ` Eric Biggers
2023-05-15 5:38 ` Kent Overstreet
2023-05-15 6:13 ` Eric Biggers
2023-05-15 6:18 ` Kent Overstreet
2023-05-15 7:13 ` Eric Biggers
2023-05-15 7:26 ` Kent Overstreet
2023-05-21 21:33 ` Eric Biggers
2023-05-21 22:04 ` Kent Overstreet
2023-05-15 10:29 ` David Laight
2023-05-10 11:56 ` David Laight
2023-05-09 21:43 ` Darrick J. Wong
2023-05-09 21:54 ` Kent Overstreet
2023-05-11 5:33 ` Theodore Ts'o
2023-05-11 5:44 ` Kent Overstreet
2023-05-13 13:25 ` Lorenzo Stoakes
2023-05-14 18:39 ` Christophe Leroy
2023-05-14 23:43 ` Kent Overstreet
2023-05-15 4:45 ` Christophe Leroy
2023-05-15 5:02 ` Kent Overstreet
2023-05-10 14:18 ` Christophe Leroy
2023-05-10 15:05 ` Johannes Thumshirn
2023-05-11 22:28 ` Kees Cook
2023-05-12 18:41 ` Kent Overstreet
2023-05-16 21:02 ` Kees Cook
2023-05-16 21:20 ` Kent Overstreet
2023-05-16 21:47 ` Matthew Wilcox
2023-05-16 21:57 ` Kent Overstreet
2023-05-17 5:28 ` Kent Overstreet
2023-05-17 14:04 ` Mike Rapoport
2023-05-17 14:18 ` Kent Overstreet
2023-05-17 15:44 ` Mike Rapoport
2023-05-17 15:59 ` Kent Overstreet
2023-06-17 4:13 ` Andy Lutomirski
2023-06-17 15:34 ` Kent Overstreet
2023-06-17 19:19 ` Andy Lutomirski
2023-06-17 20:08 ` Kent Overstreet
2023-06-17 20:35 ` Andy Lutomirski
2023-06-19 19:45 ` Kees Cook
2023-06-20 0:39 ` Kent Overstreet
2023-06-19 9:19 ` Mark Rutland
2023-06-19 10:47 ` Kent Overstreet
2023-06-19 12:47 ` Mark Rutland
2023-06-19 19:17 ` Kent Overstreet
2023-06-20 17:42 ` Andy Lutomirski
2023-06-20 18:08 ` Kent Overstreet
2023-06-20 18:15 ` Andy Lutomirski
2023-06-20 18:48 ` Dave Hansen
2023-06-20 20:18 ` Kent Overstreet
2023-06-20 20:42 ` Andy Lutomirski
2023-06-20 22:32 ` Andy Lutomirski
2023-06-20 22:43 ` Nadav Amit
2023-06-21 1:27 ` Andy Lutomirski
2023-05-09 16:56 ` [PATCH 08/32] fs: factor out d_mark_tmpfile() Kent Overstreet
2023-05-09 16:56 ` [PATCH 09/32] block: Add some exports for bcachefs Kent Overstreet
2023-05-09 16:56 ` [PATCH 10/32] block: Allow bio_iov_iter_get_pages() with bio->bi_bdev unset Kent Overstreet
2023-05-09 16:56 ` [PATCH 11/32] block: Bring back zero_fill_bio_iter Kent Overstreet
2023-05-09 16:56 ` [PATCH 12/32] block: Rework bio_for_each_segment_all() Kent Overstreet
2023-05-09 16:56 ` [PATCH 13/32] block: Rework bio_for_each_folio_all() Kent Overstreet
2023-05-09 16:56 ` [PATCH 14/32] block: Don't block on s_umount from __invalidate_super() Kent Overstreet
2023-05-09 16:56 ` [PATCH 15/32] bcache: move closures to lib/ Kent Overstreet
2023-05-10 1:10 ` Randy Dunlap
2023-05-09 16:56 ` [PATCH 16/32] MAINTAINERS: Add entry for closures Kent Overstreet
2023-05-09 17:05 ` Coly Li
2023-05-09 21:03 ` Randy Dunlap
2023-05-09 16:56 ` [PATCH 17/32] closures: closure_wait_event() Kent Overstreet
2023-05-09 16:56 ` [PATCH 18/32] closures: closure_nr_remaining() Kent Overstreet
2023-05-09 16:56 ` [PATCH 19/32] closures: Add a missing include Kent Overstreet
2023-05-09 16:56 ` [PATCH 20/32] vfs: factor out inode hash head calculation Kent Overstreet
2023-05-23 9:27 ` (subset) " Christian Brauner
2023-05-23 22:53 ` Dave Chinner
2023-05-24 6:44 ` Christoph Hellwig
2023-05-24 7:35 ` Dave Chinner
2023-05-24 8:31 ` Christian Brauner
2023-05-24 8:41 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 21/32] hlist-bl: add hlist_bl_fake() Kent Overstreet
2023-05-10 4:48 ` Dave Chinner
2023-05-23 9:27 ` (subset) " Christian Brauner
2023-05-09 16:56 ` [PATCH 22/32] vfs: inode cache conversion to hash-bl Kent Overstreet
2023-05-10 4:45 ` Dave Chinner
2023-05-16 15:45 ` Christian Brauner
2023-05-16 16:17 ` Kent Overstreet
2023-05-16 23:15 ` Dave Chinner
2023-05-22 13:04 ` Christian Brauner
2023-05-23 9:28 ` (subset) " Christian Brauner
2023-10-19 15:30 ` Mateusz Guzik
2023-10-19 15:59 ` Mateusz Guzik
2023-10-20 11:38 ` Dave Chinner
2023-10-20 17:49 ` Mateusz Guzik
2023-10-21 12:13 ` Mateusz Guzik [this message]
2023-10-23 5:10 ` Dave Chinner
2023-10-27 17:13 ` Mateusz Guzik
2023-10-27 18:36 ` Darrick J. Wong
2023-10-31 11:02 ` Christian Brauner
2023-10-31 11:31 ` Mateusz Guzik
2023-11-02 2:36 ` Kent Overstreet
2023-11-04 20:51 ` Dave Chinner
2023-05-09 16:56 ` [PATCH 23/32] iov_iter: copy_folio_from_iter_atomic() Kent Overstreet
2023-05-10 2:20 ` kernel test robot
2023-05-11 2:08 ` kernel test robot
2023-05-09 16:56 ` [PATCH 24/32] MAINTAINERS: Add entry for generic-radix-tree Kent Overstreet
2023-05-09 21:03 ` Randy Dunlap
2023-05-09 16:56 ` [PATCH 25/32] lib/generic-radix-tree.c: Don't overflow in peek() Kent Overstreet
2023-05-09 16:56 ` [PATCH 26/32] lib/generic-radix-tree.c: Add a missing include Kent Overstreet
2023-05-09 16:56 ` [PATCH 27/32] lib/generic-radix-tree.c: Add peek_prev() Kent Overstreet
2023-05-09 16:56 ` [PATCH 28/32] stacktrace: Export stack_trace_save_tsk Kent Overstreet
2023-06-19 9:10 ` Mark Rutland
2023-06-19 11:16 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 29/32] lib/string_helpers: string_get_size() now returns characters wrote Kent Overstreet
2023-07-12 19:58 ` Kees Cook
2023-07-12 20:19 ` Kent Overstreet
2023-07-12 22:38 ` Kees Cook
2023-07-12 23:53 ` Kent Overstreet
2023-07-12 20:23 ` Kent Overstreet
2023-05-09 16:56 ` [PATCH 30/32] lib: Export errname Kent Overstreet
2023-05-09 16:56 ` [PATCH 31/32] lib: add mean and variance module Kent Overstreet
2023-05-09 16:56 ` [PATCH 32/32] MAINTAINERS: Add entry for bcachefs Kent Overstreet
2023-05-09 21:04 ` Randy Dunlap
2023-05-09 21:07 ` Kent Overstreet
2023-06-15 20:41 ` [PATCH 00/32] bcachefs - a new COW filesystem Pavel Machek
2023-06-15 21:26 ` Kent Overstreet
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