From: Al Viro <viro@zeniv.linux.org.uk>
To: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>,
Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC] what to do with IOCB_DSYNC?
Date: Sun, 22 May 2022 19:04:36 +0000 [thread overview]
Message-ID: <YoqJROtrPpXWv948@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <737a889f-93b9-039f-7708-c15a21fbca2a@kernel.dk>
On Sun, May 22, 2022 at 12:48:20PM -0600, Jens Axboe wrote:
> On 5/22/22 12:39 PM, Al Viro wrote:
> > On Sun, May 22, 2022 at 12:29:16PM -0600, Jens Axboe wrote:
> >> It was sent out as a discussion point, it's not a submission and it's by
> >> no means complete (as mentioned!). If you're working on this, I'd be
> >> happy to drop it, it's not like I really enjoy the iov_iter code... And
> >> it sounds like you are?
> >
> > *snort*
> >
> > Yes, I am working on it. As for enjoying that thing... I'm not fond of
>
> OK great, I'll abandon this sandbox. Let me know when you have something
> to test, and I can compare some numbers between non-iter, iter,
> iter-with-ubuf.
>
> > forests of macros, to put it mildly. Even in the trimmed form it still
> > stinks, and places like copy_page_to_iter for iovec are still fucking
> > awful wrt misguided microoptimization attempts - mine, at that, so I've
> > nobody else to curse ;-/
>
> And it's not even clear which ones won't work with the generic variants,
> and which ones are just an optimization. I suspect a lot of the icache
> bloat from this just makes things worse...
???
copy_page_{from,to}_iter() iovec side is needed not for the sake of
optimizations - if you look at the generic variant, you'll see that it's
basically "kmap_local_page + copy_{to,from}_iter() for the contents +
kunmap_local_page", which obviously relies upon the copy_{to,from}_iter()
being non-blocking. So iovec part of it genuinely needs to differ from
the generic variant; it's just that on top of that it had been (badly)
microoptimized. So were iterators, but that got at least somewhat cleaned
up a while ago. And no, turning that into indirect calls ended up with
arseloads of overhead, more's the pity...
Anyway, at the moment I have something that builds; hadn't tried to boot it yet.
next prev parent reply other threads:[~2022-05-22 19:04 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 0:46 [RFC] what to do with IOCB_DSYNC? Al Viro
2021-06-21 13:59 ` Christoph Hellwig
2021-06-21 14:03 ` Matthew Wilcox
2021-06-21 14:09 ` Christoph Hellwig
2021-06-21 14:16 ` Matthew Wilcox
2021-06-21 14:22 ` Christoph Hellwig
2021-06-21 14:32 ` Al Viro
2021-06-21 14:35 ` Christoph Hellwig
2021-06-21 15:22 ` Jens Axboe
2022-05-21 17:48 ` Al Viro
2022-05-21 19:03 ` Jens Axboe
2022-05-21 22:14 ` Jens Axboe
2022-05-22 7:45 ` Christoph Hellwig
2022-05-22 10:23 ` Matthew Wilcox
2022-05-22 10:36 ` Al Viro
2022-05-22 11:15 ` Matthew Wilcox
2022-05-22 11:45 ` Christoph Hellwig
2022-05-22 12:39 ` Jens Axboe
2022-05-22 12:48 ` Al Viro
2022-05-22 13:02 ` Jens Axboe
2022-05-22 13:07 ` Al Viro
2022-05-22 13:09 ` Jens Axboe
2022-05-22 18:06 ` Jens Axboe
2022-05-22 18:25 ` Al Viro
2022-05-22 18:29 ` Jens Axboe
2022-05-22 18:39 ` Al Viro
2022-05-22 18:48 ` Jens Axboe
2022-05-22 19:04 ` Al Viro [this message]
2022-05-22 20:03 ` Jens Axboe
2022-05-23 0:42 ` Al Viro
2022-05-23 1:22 ` Jens Axboe
2022-05-23 1:28 ` Jens Axboe
2022-05-23 1:50 ` Jens Axboe
2022-05-23 2:43 ` Jens Axboe
2022-05-23 14:22 ` Al Viro
2022-05-23 14:34 ` Jens Axboe
2022-05-23 14:47 ` Al Viro
2022-05-23 15:12 ` Jens Axboe
2022-05-23 15:44 ` Jens Axboe
2022-05-23 15:49 ` Matthew Wilcox
2022-05-23 15:55 ` Jens Axboe
2022-05-23 16:03 ` Jens Axboe
2022-05-26 14:46 ` Jason A. Donenfeld
2022-05-27 10:09 ` Ingo Molnar
2022-05-27 10:15 ` Jason A. Donenfeld
2022-05-27 14:45 ` Samuel Neves
2022-05-27 10:25 ` Ingo Molnar
2022-05-27 10:36 ` Borislav Petkov
2022-05-28 20:54 ` Sedat Dilek
2022-05-28 20:38 ` Sedat Dilek
2022-05-28 20:39 ` Sedat Dilek
2022-05-23 16:15 ` Al Viro
2022-05-25 14:34 ` Matthew Wilcox
2022-05-26 23:19 ` Al Viro
2022-05-27 14:51 ` Jens Axboe
2022-05-22 12:21 ` Al Viro
2022-05-22 7:43 ` Christoph Hellwig
2022-05-22 12:41 ` Al Viro
2022-05-22 12:51 ` Christoph Hellwig
2021-06-21 14:22 ` Al Viro
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