Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210817202146.3218-1-shy828301@gmail.com> <CAHbLzkpkDXyEZ2izMwpkwLg9fN7qsQ+soR+iu6sd8RfOSqhS-A@mail.gmail.com>
 <20210831233839.afaenhn32nx6m2fq@box.shutemov.name> <CAHbLzkrXOM0Ow3YbZnj9RyvTJ8fwaUCzAizOMR5MP=TkxeLywg@mail.gmail.com>
 <07fd6599-88cc-e353-26f0-5de3eeea5b9f@suse.cz>
In-Reply-To: <07fd6599-88cc-e353-26f0-5de3eeea5b9f@suse.cz>
From:   Yang Shi <shy828301@gmail.com>
Date:   Wed, 1 Sep 2021 10:25:53 -0700
Message-ID: <CAHbLzkoHghYQaqridYuWY=YUm4AB7sQDbCjbmGgr5iXx=nsETg@mail.gmail.com>
Subject: Re: [RFC PATCH] mm: khugepaged: don't carry huge page to the next
 loop for !CONFIG_NUMA
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        Hugh Dickins <hughd@google.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Sep 1, 2021 at 3:26 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 9/1/21 05:46, Yang Shi wrote:
> > On Tue, Aug 31, 2021 at 4:38 PM Kirill A. Shutemov <kirill@shutemov.name> wrote:
> >>
> >> On Mon, Aug 30, 2021 at 11:49:43AM -0700, Yang Shi wrote:
> >> > Gently ping...
> >> >
> >> > Does this patch make sense? BTW, I have a couple of other khugepaged
> >> > related patches in my queue. I plan to send them with this patch
> >> > together. It would be great to hear some feedback before resending
> >> > this one.
> >>
> >> I don't really care for !NUMA optimization. I believe that most of setups
> >> that benefit from THP has NUMA enabled compile time.
> >
> > Agreed.
> >
> >>
> >> But if you wanna to go this path, make an effort to cleanup other
> >> artifacts for the !NUMA optimization: the ifdef has to be gone and all
> >> callers of these helpers has to be revisited. There's more opportunities to
> >> cleanup. Like it is very odd that khugepaged_prealloc_page() frees the
> >> page.
> >
> > Yes, they are gone in this patch. The only remaining for !NUMA is
> > khugepaged_find_target_node() which just returns 0.
>
> As Kirill pointed out, there's also khugepaged_prealloc_page() where the
> only remaining variant does actually no preallocation, just freeing of an
> unused page and some kind of "sleep after first alloc fail, break after
> second alloc fail" logic.
> This could now be moved to khugepaged_do_scan() loop itself and maybe it
> will be easier to follow.

Aha, I see. Misunderstood him. I'm supposed that you mean move into
khugepaged_scan_mm_slot().

>
> >>
> >>
> >> --
> >>  Kirill A. Shutemov
> >
>