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: <CAG48ez3YavBAO1nQquca6W-RvH4yy2B7oiY4jWn96B_aaA_gVw@mail.gmail.com>
Date:   Fri, 22 Jan 2021 14:09:33 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Christoph Lameter <cl@...ux.com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        aneesh.kumar@...ux.ibm.com, Michal Hocko <mhocko@...nel.org>
Subject: Re: [RFC PATCH v0] mm/slub: Let number of online CPUs determine the
 slub page order

On Fri, Jan 22, 2021 at 2:05 PM Jann Horn <jannh@...gle.com> wrote:
> On Thu, Jan 21, 2021 at 7:19 PM Vlastimil Babka <vbabka@...e.cz> wrote:
> > On 1/21/21 11:01 AM, Christoph Lameter wrote:
> > > On Thu, 21 Jan 2021, Bharata B Rao wrote:
> > >
> > >> > The problem is that calculate_order() is called a number of times
> > >> > before secondaries CPUs are booted and it returns 1 instead of 224.
> > >> > This makes the use of num_online_cpus() irrelevant for those cases
> > >> >
> > >> > After adding in my command line "slub_min_objects=36" which equals to
> > >> > 4 * (fls(num_online_cpus()) + 1) with a correct num_online_cpus == 224
> > >> > , the regression diseapears:
> > >> >
> > >> > 9 iterations of hackbench -l 16000 -g 16: 3.201sec (+/- 0.90%)
> >
> > I'm surprised that hackbench is that sensitive to slab performance, anyway. It's
> > supposed to be a scheduler benchmark? What exactly is going on?
>
> Uuuh, I think powerpc doesn't have cmpxchg_double?
>
> "vgrep cmpxchg_double arch/" just spits out arm64, s390 and x86? And
> <https://liblfds.org/mediawiki/index.php?title=Article:CAS_and_LL/SC_Implementation_Details_by_Processor_family>
> says under "POWERPC": "no DW LL/SC"
>
> So powerpc is probably hitting the page-bitlock-based implementation
> all the time for stuff like __slub_free()? Do you have detailed
> profiling results from "perf top" or something like that?
>
> (I actually have some WIP patches and a design document for getting
> rid of cmpxchg_double in struct page that I hacked together in the
> last couple days; I'm currently in the process of sending them over to
> some other folks in the company who hopefully have cycles to
> review/polish/benchmark them so that they can be upstreamed, assuming
> that those folks think they're important enough. I don't have the
> cycles for it...)

(The stuff I have in mind will only work on 64-bit though. We are
talking about PPC64 here, right?)

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ