linux-kernel - Re: [PATCH 0/7] padata: parallelize deferred page init

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Message-ID: <20200501024840.eofsy3av5bwcdpw2@ca-dmjordan1.us.oracle.com>
Date:   Thu, 30 Apr 2020 22:48:40 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Josh Triplett <josh@...htriplett.org>
Cc:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jonathan Corbet <corbet@....net>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Michal Hocko <mhocko@...nel.org>, Pavel Machek <pavel@....cz>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Shile Zhang <shile.zhang@...ux.alibaba.com>,
        Tejun Heo <tj@...nel.org>, Zi Yan <ziy@...dia.com>,
        linux-crypto@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/7] padata: parallelize deferred page init

On Thu, Apr 30, 2020 at 06:09:35PM -0700, Josh Triplett wrote:
> On Thu, Apr 30, 2020 at 04:11:18PM -0400, Daniel Jordan wrote:
> > Sometimes the kernel doesn't take full advantage of system memory
> > bandwidth, leading to a single CPU spending excessive time in
> > initialization paths where the data scales with memory size.
> > 
> > Multithreading naturally addresses this problem, and this series is the
> > first step.
> > 
> > It extends padata, a framework that handles many parallel singlethreaded
> > jobs, to handle multithreaded jobs as well by adding support for
> > splitting up the work evenly, specifying a minimum amount of work that's
> > appropriate for one helper thread to do, load balancing between helpers,
> > and coordinating them.  More documentation in patches 4 and 7.
> > 
> > The first user is deferred struct page init, a large bottleneck in
> > kernel boot--actually the largest for us and likely others too.  This
> > path doesn't require concurrency limits, resource control, or priority
> > adjustments like future users will (vfio, hugetlb fallocate, munmap)
> > because it happens during boot when the system is otherwise idle and
> > waiting on page init to finish.
> > 
> > This has been tested on a variety of x86 systems and speeds up kernel
> > boot by 6% to 49% by making deferred init 63% to 91% faster.  Patch 6
> > has detailed numbers.  Test results from other systems appreciated.
> > 
> > This series is based on v5.6 plus these three from mmotm:
> > 
> >   mm-call-touch_nmi_watchdog-on-max-order-boundaries-in-deferred-init.patch
> >   mm-initialize-deferred-pages-with-interrupts-enabled.patch
> >   mm-call-cond_resched-from-deferred_init_memmap.patch
> > 
> > All of the above can be found in this branch:
> > 
> >   git://oss.oracle.com/git/linux-dmjordan.git padata-mt-definit-v1
> >   https://oss.oracle.com/git/gitweb.cgi?p=linux-dmjordan.git;a=shortlog;h=refs/heads/padata-mt-definit-v1
> 
> For the series (and the three prerequisite patches):
> 
> Tested-by: Josh Triplett <josh@...htriplett.org>

Appreciate the runs, Josh, thanks.