linux-kernel - Re: [PATCH v4 00/40] lib/find: add atomic find

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZnR1tQN01kN97G_F@yury-ThinkPad>
Date: Thu, 20 Jun 2024 11:32:21 -0700
From: Yury Norov <yury.norov@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	"Md. Haris Iqbal" <haris.iqbal@...os.com>,
	Akinobu Mita <akinobu.mita@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Chaitanya Kulkarni <kch@...dia.com>,
	Christian Brauner <brauner@...nel.org>,
	Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Disseldorp <ddiss@...e.de>,
	Edward Cree <ecree.xilinx@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gregory Greenman <gregory.greenman@...el.com>,
	Hans Verkuil <hverkuil@...all.nl>,
	Hans de Goede <hdegoede@...hat.com>,
	Hugh Dickins <hughd@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
	Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
	Jiri Pirko <jiri@...nulli.us>, Jiri Slaby <jirislaby@...nel.org>,
	Kalle Valo <kvalo@...nel.org>, Karsten Graul <kgraul@...ux.ibm.com>,
	Karsten Keil <isdn@...ux-pingi.de>,
	Kees Cook <keescook@...omium.org>,
	Leon Romanovsky <leon@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Martin Habets <habetsm.xilinx@...il.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Michal Simek <monstr@...str.eu>,
	Nicholas Piggin <npiggin@...il.com>,
	Oliver Neukum <oneukum@...e.com>, Paolo Abeni <pabeni@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ping-Ke Shih <pkshih@...ltek.com>, Rich Felker <dalias@...c.org>,
	Rob Herring <robh@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Sean Christopherson <seanjc@...gle.com>,
	Shuai Xue <xueshuai@...ux.alibaba.com>,
	Stanislaw Gruszka <stf_xl@...pl>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Wenjia Zhang <wenjia@...ux.ibm.com>, Will Deacon <will@...nel.org>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	GR-QLogic-Storage-Upstream@...vell.com, alsa-devel@...a-project.org,
	ath10k@...ts.infradead.org, dmaengine@...r.kernel.org,
	iommu@...ts.linux.dev, kvm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
	linux-block@...r.kernel.org, linux-bluetooth@...r.kernel.org,
	linux-hyperv@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
	linux-media@...r.kernel.org, linux-mips@...r.kernel.org,
	linux-net-drivers@....com, linux-pci@...r.kernel.org,
	linux-rdma@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-sound@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-wireless@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, mpi3mr-linuxdrv.pdl@...adcom.com,
	netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org,
	Alexey Klimov <alexey.klimov@...aro.org>,
	Bart Van Assche <bvanassche@....org>, Jan Kara <jack@...e.cz>,
	Matthew Wilcox <willy@...radead.org>,
	Mirsad Todorovac <mirsad.todorovac@....unizg.hr>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Shtylyov <s.shtylyov@....ru>
Subject: Re: [PATCH v4 00/40] lib/find: add atomic find_bit() primitives

On Thu, Jun 20, 2024 at 11:00:38AM -0700, Linus Torvalds wrote:
> On Thu, 20 Jun 2024 at 10:57, Yury Norov <yury.norov@...il.com> wrote:
> >
> >
> > The typical lock-protected bit allocation may look like this:
> 
> If it looks like this, then nobody cares. Clearly the user in question
> never actually cared about performance, and you SHOULD NOT then say
> "let's optimize this that nobody cares about":.
> 
> Yury, I spend an inordinate amount of time just double-checking your
> patches. I ended up having to basically undo one of them just days
> ago.

Is that in master already? I didn't get any email, and I can't find
anything related in the master branch.

> New rule: before you send some optimization, you need to have NUMBERS.

I tried to underline that it's not a performance optimization at my
best. People notice some performance differences, but it's ~3%, no
more.

> Some kind of "look, this code is visible in profiles, so we actually care".

The original motivation comes from a KCSAN report, so it's already
visible in profiles. See [1] in cover letter. This series doesn't fix
that particular issue, but it adds tooling that allow people to search
and acquire bits in bitmaps without firing KCSAN warnings.

This series fixes one real bug in the codebase - see #33, and
simplifies bitmaps usage in many other places. Many people like
it, and acked the patches.

Again, this is NOT a performance series.

Thanks,
Yury

> Because without numbers, I'm just not going to pull anything from you.
> These insane inlines for things that don't matter need to stop.
> 
> And if they *DO* matter, you need to show that they matter.
> 
>                Linus