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: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAHk-=wjgaWEsObv2SO-xa6g6ncj53q8tPpM3cgJGr+wtWknVyA@mail.gmail.com>
Date:   Fri, 14 Oct 2022 13:44:25 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Isaac Manjarres <isaacmanjarres@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ard Biesheuvel <ardb@...nel.org>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>, kernel-team@...roid.com
Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN

On Fri, Oct 14, 2022 at 1:24 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> Agreed. Even allowing a 64-byte kmalloc cache on a system with a
> 64-byte cacheline size saves quite a bit of memory.

Well, the *really* trivial thing to do is to just say "if the platform
is DMA coherent, just allow any size kmalloc cache". And just
consciously leave the broken garbage behind.

Because it's not just 64-byte kmalloc. It's things like 'avtab_node'
that is 24 bytes, and that on my system currently uses about 3MB of
memory simply because there's a _lot_ of them.

I've got 1.8MB in "kmalloc-32" too, and about 1MB in "kamlloc-16", fwiw. That's

Yeah, yeah, this is on a 64GB machine and so none of that matters (and
some of these things are very much "scales with memory", but these
small allocations aren't actually all that unusual.

And yes, the above is obviously on my x86-64 machine.

My arm64 laptop doesn't have the small kmallocs, and as a result the
"kmalloc-128" has 633 _thousand_ entries, and takes up 77MB of RAM on
my 16GB laptop. I'm assuming (but have no proof) more than 50% of that
is just wasted memory.

I suspect that DMA is cache coherent on this thing, and that wasted
space is just *stupid* wasted space, but hey, I don't actually know. I
just use the Asahi people's patches.

               Linus

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ