Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 26 Mar 2020 14:58:22 -0400
From:   Daniel Jordan <daniel.m.jordan@oracle.com>
To:     Shile Zhang <shile.zhang@linux.alibaba.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] mm: fix tick timer stall during deferred page init
Message-ID: <20200326185822.6n56yl2llvdranur@ca-dmjordan1.us.oracle.com>
References: <20200311123848.118638-1-shile.zhang@linux.alibaba.com>
 <20200319190512.cwnvgvv3upzcchkm@ca-dmjordan1.us.oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200319190512.cwnvgvv3upzcchkm@ca-dmjordan1.us.oracle.com>
User-Agent: NeoMutt/20180716
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Mar 19, 2020 at 03:05:12PM -0400, Daniel Jordan wrote:
> Regardless,
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>

Darn, I spoke too soon.

On a two-socket Xeon, smaller values of TICK_PAGE_COUNT caused the deferred
init timestamp to grow by over 25%.  This was with pgdatinit0 bound to the
timer interrupt CPU to make sure the issue always reproduces.

               TICK_PAGE_COUNT     node 0 deferred
                                   init time (ms)
               ---------------     ---------------
                          4096                 610
                          8192                 587
                         16384                 487
                         32768                 480    // used in the patch

Instead of trying to find a constant that lets the timer interrupt run often
enough, I think a better way forward is to reconsider how we handle the resize
lock.  I plan to prototype something and reply back with what I get.