From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] block: switch to atomic_t for request references
Date: Tue, 7 Dec 2021 08:03:20 -0800 [thread overview]
Message-ID: <CAHk-=wh6NyZeMEfw8YDyqCeoev7X319DDF41p0YSJFVNEkVQfw@mail.gmail.com> (raw)
In-Reply-To: <Ya8qptlJ4yLVUSBi@hirez.programming.kicks-ass.net>
On Tue, Dec 7, 2021 at 1:34 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> Now, it could be GCC generates atrociously bad code simply because it
> doesn't know it can use the flags from the XADD in which case we can
> look at doing an arch asm implementation.
That may help.
This thread started because of alleged performance problems with
refcount_t. No numbers, and maybe it was wrong, but they have been
seen before, so I wouldn't dismiss the issue.
What I've seen personally is the horrendous "multiple different calls
to overflow functions with different arguments", which makes
__refcount_add() do stupid things and blow up the code. All for
entirely pointless debugging code.
Linus
next prev parent reply other threads:[~2021-12-07 16:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-03 15:35 [PATCH] block: switch to atomic_t for request references Jens Axboe
2021-12-03 15:56 ` Keith Busch
2021-12-06 6:53 ` Christoph Hellwig
2021-12-06 8:31 ` Peter Zijlstra
2021-12-06 16:32 ` Jens Axboe
2021-12-06 17:19 ` Peter Zijlstra
2021-12-06 17:35 ` Linus Torvalds
2021-12-06 18:13 ` Jens Axboe
2021-12-06 20:51 ` Kees Cook
2021-12-06 21:17 ` Linus Torvalds
2021-12-06 23:28 ` Kees Cook
2021-12-07 0:13 ` Linus Torvalds
2021-12-07 4:56 ` Kees Cook
2021-12-07 9:34 ` Peter Zijlstra
2021-12-07 16:03 ` Linus Torvalds [this message]
2021-12-07 10:30 ` Peter Zijlstra
2021-12-07 16:10 ` Linus Torvalds
2021-12-07 16:23 ` Peter Zijlstra
2021-12-06 16:31 ` Jens Axboe
2021-12-07 11:26 ` Peter Zijlstra
2021-12-07 13:28 ` Peter Zijlstra
2021-12-07 15:51 ` Peter Zijlstra
2021-12-07 16:13 ` Linus Torvalds
2021-12-07 16:52 ` Peter Zijlstra
2021-12-07 17:41 ` Peter Zijlstra
2021-12-07 17:43 ` Linus Torvalds
2021-12-07 17:45 ` Linus Torvalds
2021-12-07 20:28 ` Peter Zijlstra
2021-12-07 23:23 ` Linus Torvalds
2021-12-08 17:07 ` Peter Zijlstra
2021-12-08 18:00 ` Linus Torvalds
2021-12-08 18:44 ` Peter Zijlstra
2021-12-08 18:50 ` Linus Torvalds
2021-12-08 20:32 ` Peter Zijlstra
2021-12-10 10:57 ` Peter Zijlstra
2021-12-10 12:38 ` Peter Zijlstra
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