All of lore.kernel.org
 help / color / mirror / Atom feed
From: Minchan Kim <minchan@kernel.org>
To: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	cgoldswo@codeaurora.org, linux-fsdevel@vger.kernel.org,
	david@redhat.com, vbabka@suse.cz, viro@zeniv.linux.org.uk,
	joaodias@google.com
Subject: Re: [RFC 1/2] mm: disable LRU pagevec during the migration temporarily
Date: Thu, 18 Feb 2021 07:52:25 -0800	[thread overview]
Message-ID: <YC6NOVBy5J4bUjfD@google.com> (raw)
In-Reply-To: <YC4ifqXYEeWrj4aF@dhcp22.suse.cz>

On Thu, Feb 18, 2021 at 09:17:02AM +0100, Michal Hocko wrote:
> On Wed 17-02-21 13:32:05, Minchan Kim wrote:
> > On Wed, Feb 17, 2021 at 09:16:12PM +0000, Matthew Wilcox wrote:
> > > On Wed, Feb 17, 2021 at 12:46:19PM -0800, Minchan Kim wrote:
> > > > > I suspect you do not want to add atomic_read inside hot paths, right? Is
> > > > > this really something that we have to microoptimize for? atomic_read is
> > > > > a simple READ_ONCE on many archs.
> > > > 
> > > > It's also spin_lock_irq_save in some arch. If the new synchonization is
> > > > heavily compilcated, atomic would be better for simple start but I thought
> > > > this locking scheme is too simple so no need to add atomic operation in
> > > > readside.
> > > 
> > > What arch uses a spinlock for atomic_read()?  I just had a quick grep and
> > > didn't see any.
> > 
> > Ah, my bad. I was confused with update side.
> > Okay, let's use atomic op to make it simple.
> 
> Thanks. This should make the code much more simple. Before you send
> another version for the review I have another thing to consider. You are
> kind of wiring this into the migration code but control over lru pcp
> caches can be used in other paths as well. Memory offlining would be
> another user. We already disable page allocator pcp caches to prevent
> regular draining. We could do the same with lru pcp caches.

I didn't catch your point here. If memory offlining is interested on
disabling lru pcp, it could call migrate_prep and migrate_finish
like other places. Are you suggesting this one?

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a969463bdda4..0ec1c13bfe32 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1425,8 +1425,12 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
                node_clear(mtc.nid, nmask);
                if (nodes_empty(nmask))
                        node_set(mtc.nid, nmask);
+
+               migrate_prep();
                ret = migrate_pages(&source, alloc_migration_target, NULL,
                        (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
+
+               migrate_finish();
                if (ret) {
                        list_for_each_entry(page, &source, lru) {
                                pr_warn("migrating pfn %lx failed ret:%d ",


  parent reply	other threads:[~2021-02-18 18:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-16 17:03 [RFC 1/2] mm: disable LRU pagevec during the migration temporarily Minchan Kim
2021-02-16 17:03 ` [RFC 2/2] mm: fs: Invalidate BH LRU during page migration Minchan Kim
2021-02-16 18:22 ` [RFC 1/2] mm: disable LRU pagevec during the migration temporarily Matthew Wilcox
2021-02-16 21:30   ` Minchan Kim
2021-02-17  8:59 ` Michal Hocko
2021-02-17  9:50   ` Michal Hocko
2021-02-17 20:51     ` Minchan Kim
2021-02-17 21:11       ` Matthew Wilcox
2021-02-17 21:22         ` Minchan Kim
2021-02-17 20:46   ` Minchan Kim
2021-02-17 21:16     ` Matthew Wilcox
2021-02-17 21:32       ` Minchan Kim
2021-02-18  8:17         ` Michal Hocko
2021-02-18  8:24           ` David Hildenbrand
2021-02-18 15:52           ` Minchan Kim [this message]
2021-02-18 16:08             ` Michal Hocko
2021-02-18 16:21               ` Minchan Kim

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YC6NOVBy5J4bUjfD@google.com \
    --to=minchan@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=cgoldswo@codeaurora.org \
    --cc=david@redhat.com \
    --cc=joaodias@google.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@suse.com \
    --cc=vbabka@suse.cz \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.