From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Howells <dhowells@redhat.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 01/29] iov_iter: Switch to using a table of operations
Date: Sat, 21 Nov 2020 10:21:17 -0800 [thread overview]
Message-ID: <CAHk-=wjttbQzVUR-jSW-Q42iOUJtu4zCxYe9HO3ovLGOQ_3jSA@mail.gmail.com> (raw)
In-Reply-To: <160596801020.154728.15935034745159191564.stgit@warthog.procyon.org.uk>
On Sat, Nov 21, 2020 at 6:13 AM David Howells <dhowells@redhat.com> wrote:
>
> Switch to using a table of operations. In a future patch the individual
> methods will be split up by type. For the moment, however, the ops tables
> just jump directly to the old functions - which are now static. Inline
> wrappers are provided to jump through the hooks.
So I think conceptually this is the right thing to do, but I have a
couple of worries:
- do we really need all those different versions? I'm thinking
"iter_full" versions in particular. They I think the iter_full version
could just be wrappers that call the regular iter thing and verify the
end result is full (and revert if not). No?
- I don't like the xxx_iter_op naming - even as a temporary thing.
Please don't use "xxx" as a placeholder. It's not a great grep
pattern, it's not really descriptive, and we've literally had issues
with things being marked as spam when you use that. So it's about the
worst pattern to use.
Use "anycase" - or something like that - which is descriptive and
greps much better (ie not a single hit for that pattern in the kernel
either before or after).
- I worry a bit about the indirect call overhead and spectre v2.
So yeah, it would be good to have benchmarks to make sure this
doesn't regress for some simple case.
Other than those things, my initial reaction is "this does seem cleaner".
Al?
Linus
next prev parent reply other threads:[~2020-11-21 18:21 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-21 14:13 [PATCH 00/29] RFC: iov_iter: Switch to using an ops table David Howells
2020-11-21 14:13 ` [PATCH 01/29] iov_iter: Switch to using a table of operations David Howells
2020-11-21 14:31 ` Pavel Begunkov
2020-11-23 23:21 ` Pavel Begunkov
2020-11-21 18:21 ` Linus Torvalds [this message]
2020-12-11 1:30 ` Al Viro
2020-11-22 13:33 ` David Howells
2020-11-22 13:58 ` David Laight
2020-11-22 19:22 ` Linus Torvalds
2020-11-22 22:34 ` David Laight
2020-11-22 22:46 ` David Laight
2020-11-23 8:05 ` Christoph Hellwig
2020-11-23 10:31 ` David Howells
2020-11-23 23:42 ` Pavel Begunkov
2020-11-24 12:50 ` David Howells
2020-11-24 15:30 ` Jens Axboe
2020-11-27 17:14 ` David Howells
2020-11-23 11:14 ` David Howells
[not found] ` <20201203064536.GE27350@xsang-OptiPlex-9020>
2020-12-03 17:47 ` [iov_iter] 9bd0e337c6: will-it-scale.per_process_ops -4.8% regression Linus Torvalds
2020-12-03 17:50 ` Jens Axboe
2020-12-04 11:50 ` David Howells
2020-12-04 11:51 ` David Howells
2020-12-07 13:10 ` Oliver Sang
2020-12-07 13:20 ` David Howells
2020-11-21 14:13 ` [PATCH 02/29] iov_iter: Split copy_page_to_iter() David Howells
2020-11-21 14:13 ` [PATCH 03/29] iov_iter: Split iov_iter_fault_in_readable David Howells
2020-11-21 14:13 ` [PATCH 04/29] iov_iter: Split the iterate_and_advance() macro David Howells
2020-11-21 14:14 ` [PATCH 05/29] iov_iter: Split copy_to_iter() David Howells
2020-11-21 14:14 ` [PATCH 06/29] iov_iter: Split copy_mc_to_iter() David Howells
2020-11-21 14:14 ` [PATCH 07/29] iov_iter: Split copy_from_iter() David Howells
2020-11-21 14:14 ` [PATCH 08/29] iov_iter: Split the iterate_all_kinds() macro David Howells
2020-11-21 14:14 ` [PATCH 09/29] iov_iter: Split copy_from_iter_full() David Howells
2020-11-21 14:14 ` [PATCH 10/29] iov_iter: Split copy_from_iter_nocache() David Howells
2020-11-21 14:14 ` [PATCH 11/29] iov_iter: Split copy_from_iter_flushcache() David Howells
2020-11-21 14:14 ` [PATCH 12/29] iov_iter: Split copy_from_iter_full_nocache() David Howells
2020-11-21 14:15 ` [PATCH 13/29] iov_iter: Split copy_page_from_iter() David Howells
2020-11-21 14:15 ` [PATCH 14/29] iov_iter: Split iov_iter_zero() David Howells
2020-11-21 14:15 ` [PATCH 15/29] iov_iter: Split copy_from_user_atomic() David Howells
2020-11-21 14:15 ` [PATCH 16/29] iov_iter: Split iov_iter_advance() David Howells
2020-11-21 14:15 ` [PATCH 17/29] iov_iter: Split iov_iter_revert() David Howells
2020-11-21 14:15 ` [PATCH 18/29] iov_iter: Split iov_iter_single_seg_count() David Howells
2020-11-21 14:15 ` [PATCH 19/29] iov_iter: Split iov_iter_alignment() David Howells
2020-11-21 14:15 ` [PATCH 20/29] iov_iter: Split iov_iter_gap_alignment() David Howells
2020-11-21 14:16 ` [PATCH 21/29] iov_iter: Split iov_iter_get_pages() David Howells
2020-11-21 14:16 ` [PATCH 22/29] iov_iter: Split iov_iter_get_pages_alloc() David Howells
2020-11-21 14:16 ` [PATCH 23/29] iov_iter: Split csum_and_copy_from_iter() David Howells
2020-11-21 14:16 ` [PATCH 24/29] iov_iter: Split csum_and_copy_from_iter_full() David Howells
2020-11-21 14:16 ` [PATCH 25/29] iov_iter: Split csum_and_copy_to_iter() David Howells
2020-11-21 14:16 ` [PATCH 26/29] iov_iter: Split iov_iter_npages() David Howells
2020-11-21 14:16 ` [PATCH 27/29] iov_iter: Split dup_iter() David Howells
2020-11-21 14:17 ` [PATCH 28/29] iov_iter: Split iov_iter_for_each_range() David Howells
2020-11-21 14:17 ` [PATCH 29/29] iov_iter: Remove iterate_all_kinds() and iterate_and_advance() David Howells
2020-11-21 14:34 ` [PATCH 00/29] RFC: iov_iter: Switch to using an ops table Pavel Begunkov
2020-11-21 18:23 ` Linus Torvalds
2020-12-11 3:24 ` Matthew Wilcox
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