From: Hugh Dickins <hughd@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
atishp@atishpatra.org, peterz@infradead.org,
srikar@linux.vnet.ibm.com, valentin.schneider@arm.com,
vbabka@suse.cz, mpe@ellerman.id.au,
Palmer Dabbelt <palmerdabbelt@google.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-team@android.com,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 1/2] mm: Guard a use of node_reclaim_distance with CONFIFG_NUMA
Date: Fri, 26 Feb 2021 17:31:40 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.11.2102261724370.15322@eggly.anvils> (raw)
In-Reply-To: <20210226123716.6bc2a463e0ee9d1770c7966b@linux-foundation.org>
On Fri, 26 Feb 2021, Andrew Morton wrote:
> On Fri, 26 Feb 2021 12:17:20 -0800 Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > From: Palmer Dabbelt <palmerdabbelt@google.com>
> >
> > This is only useful under CONFIG_NUMA. IIUC skipping the check is the
> > right thing to do here, as without CONFIG_NUMA there will never be any
> > large node distances on non-NUMA systems.
> >
> > I expected this to manifest as a link failure under (!CONFIG_NUMA &&
> > CONFIG_TRANSPARENT_HUGE_PAGES), but I'm not actually seeing that. I
> > think the reference is just getting pruned before it's checked, but I
> > didn't get that from reading the code so I'm worried I'm missing
> > something.
> >
> > Either way, this is necessary to guard the definition of
> > node_reclaim_distance with CONFIG_NUMA.
> >
> > Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
> > ---
> > mm/khugepaged.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index a7d6cb912b05..b1bf191c3a54 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -819,8 +819,10 @@ static bool khugepaged_scan_abort(int nid)
> > for (i = 0; i < MAX_NUMNODES; i++) {
> > if (!khugepaged_node_load[i])
> > continue;
> > +#ifdef CONFIG_NUMA
> > if (node_distance(nid, i) > node_reclaim_distance)
> > return true;
> > +#endif
> > }
> > return false;
> > }
>
> This makes the entire loop a no-op. Perhaps Kirill can help take a
> look at removing unnecessary code in khugepaged.c when CONFIG_NUMA=n?
First lines of khugepaged_scan_abort() say
if (!node_reclaim_mode)
return false;
And include/linux/swap.h says
#ifdef CONFIG_NUMA
extern int node_reclaim_mode;
extern int sysctl_min_unmapped_ratio;
extern int sysctl_min_slab_ratio;
#else
#define node_reclaim_mode 0
#endif
So, no need for an #ifdef CONFIG_NUMA inside khugepaged_scan_abort().
Hugh
next prev parent reply other threads:[~2021-02-27 1:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 20:17 [PATCH 1/2] mm: Guard a use of node_reclaim_distance with CONFIFG_NUMA Palmer Dabbelt
2021-02-26 20:17 ` [PATCH 2/2] topology: Guard " Palmer Dabbelt
2021-02-26 20:37 ` [PATCH 1/2] mm: Guard a use of " Andrew Morton
2021-02-27 1:31 ` Hugh Dickins [this message]
2021-02-27 3:05 ` Palmer Dabbelt
2021-02-27 3:41 ` Hugh Dickins
2021-02-27 4:14 ` Palmer Dabbelt
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