From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F959C433E0 for ; Mon, 6 Jul 2020 11:35:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C775C206E9 for ; Mon, 6 Jul 2020 11:35:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="KYXVtEnD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C775C206E9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1222F6B0003; Mon, 6 Jul 2020 07:35:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0AB936B0007; Mon, 6 Jul 2020 07:35:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EB46C6B000C; Mon, 6 Jul 2020 07:35:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0082.hostedemail.com [216.40.44.82]) by kanga.kvack.org (Postfix) with ESMTP id D29AF6B0003 for ; Mon, 6 Jul 2020 07:35:38 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 5118C1EE6 for ; Mon, 6 Jul 2020 11:35:38 +0000 (UTC) X-FDA: 77007445956.04.duck22_1b03cb126eab Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin04.hostedemail.com (Postfix) with ESMTP id 172AE800296B for ; Mon, 6 Jul 2020 11:35:38 +0000 (UTC) X-HE-Tag: duck22_1b03cb126eab X-Filterd-Recvd-Size: 7467 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Mon, 6 Jul 2020 11:35:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=OEy4U14lLKI068FHS0JNccIDytAin8DP0F/8fksYMHM=; b=KYXVtEnDEU3QfsHNKDl8JD6cEA IdtyW0WG0Z/5mgR9zDgpmcd2IGC5N6d50cIM/Q3NuAxlEzPib6+8TwZ8YuBaOn/pi2sEhzNmR5hkh k5U2rRABYmgA/UOuXfSnde6iXrCiOgypj593SKiGNG1o73ZDYlrCYEDhvQL4K+FN08k+QOz9LIKEx +CHnrREONgkl9Ff10suBnwJn49Kb+Bp87ssbB+0smB+PwOaVVWwzHql4tVCNYUV7pG7Ha4pBv0xKN QslQOwWxYu8tcBZ+GfPPW/YqSwHaROA7+J57WrQ9xQR1mOtL8v1hBZlx+MKCGOrHOQ55gBh4dwUyZ 4/1VaErA==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jsPOz-00057v-Bn; Mon, 06 Jul 2020 11:35:13 +0000 Date: Mon, 6 Jul 2020 12:35:13 +0100 From: Matthew Wilcox To: Alex Shi Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, yang.shi@linux.alibaba.com, hannes@cmpxchg.org, lkp@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, shakeelb@google.com, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com Subject: Re: [PATCH v14 07/20] mm/thp: narrow lru locking Message-ID: <20200706113513.GY25523@casper.infradead.org> References: <1593752873-4493-1-git-send-email-alex.shi@linux.alibaba.com> <1593752873-4493-8-git-send-email-alex.shi@linux.alibaba.com> <124eeef1-ff2b-609e-3bf6-a118100c3f2a@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <124eeef1-ff2b-609e-3bf6-a118100c3f2a@linux.alibaba.com> X-Rspamd-Queue-Id: 172AE800296B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 06, 2020 at 05:15:09PM +0800, Alex Shi wrote: > Hi Kirill & Johannes & Matthew, >=20 > Would you like to give some comments or share your concern of this patc= hset, > specialy for THP part?=20 I don't have the brain space to understand this patch set fully at the moment. I'll note that the realtime folks are doing their best to stamp out users of local_irq_disable(), so they won't be pleased to see you adding a new one. Also, you removed the comment explaining why the lock needed to be taken. > Many Thanks > Alex >=20 > =E5=9C=A8 2020/7/3 =E4=B8=8B=E5=8D=881:07, Alex Shi =E5=86=99=E9=81=93: > > lru_lock and page cache xa_lock have no reason with current sequence, > > put them together isn't necessary. let's narrow the lru locking, but > > left the local_irq_disable to block interrupt re-entry and statistic = update. > >=20 > > Hugh Dickins point: split_huge_page_to_list() was already silly,to be > > using the _irqsave variant: it's just been taking sleeping locks, so > > would already be broken if entered with interrupts enabled. > > so we can save passing flags argument down to __split_huge_page(). > >=20 > > Signed-off-by: Alex Shi > > Signed-off-by: Wei Yang > > Cc: Hugh Dickins > > Cc: Kirill A. Shutemov > > Cc: Andrea Arcangeli > > Cc: Johannes Weiner > > Cc: Matthew Wilcox > > Cc: Andrew Morton > > Cc: linux-mm@kvack.org > > Cc: linux-kernel@vger.kernel.org > > --- > > mm/huge_memory.c | 24 ++++++++++++------------ > > 1 file changed, 12 insertions(+), 12 deletions(-) > >=20 > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index b18f21da4dac..607869330329 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2433,7 +2433,7 @@ static void __split_huge_page_tail(struct page = *head, int tail, > > } > > =20 > > static void __split_huge_page(struct page *page, struct list_head *l= ist, > > - pgoff_t end, unsigned long flags) > > + pgoff_t end) > > { > > struct page *head =3D compound_head(page); > > pg_data_t *pgdat =3D page_pgdat(head); > > @@ -2442,8 +2442,6 @@ static void __split_huge_page(struct page *page= , struct list_head *list, > > unsigned long offset =3D 0; > > int i; > > =20 > > - lruvec =3D mem_cgroup_page_lruvec(head, pgdat); > > - > > /* complete memcg works before add pages to LRU */ > > mem_cgroup_split_huge_fixup(head); > > =20 > > @@ -2455,6 +2453,11 @@ static void __split_huge_page(struct page *pag= e, struct list_head *list, > > xa_lock(&swap_cache->i_pages); > > } > > =20 > > + /* lock lru list/PageCompound, ref freezed by page_ref_freeze */ > > + spin_lock(&pgdat->lru_lock); > > + > > + lruvec =3D mem_cgroup_page_lruvec(head, pgdat); > > + > > for (i =3D HPAGE_PMD_NR - 1; i >=3D 1; i--) { > > __split_huge_page_tail(head, i, lruvec, list); > > /* Some pages can be beyond i_size: drop them from page cache */ > > @@ -2474,6 +2477,8 @@ static void __split_huge_page(struct page *page= , struct list_head *list, > > } > > =20 > > ClearPageCompound(head); > > + spin_unlock(&pgdat->lru_lock); > > + /* Caller disabled irqs, so they are still disabled here */ > > =20 > > split_page_owner(head, HPAGE_PMD_ORDER); > > =20 > > @@ -2491,8 +2496,7 @@ static void __split_huge_page(struct page *page= , struct list_head *list, > > page_ref_add(head, 2); > > xa_unlock(&head->mapping->i_pages); > > } > > - > > - spin_unlock_irqrestore(&pgdat->lru_lock, flags); > > + local_irq_enable(); > > =20 > > remap_page(head); > > =20 > > @@ -2631,12 +2635,10 @@ bool can_split_huge_page(struct page *page, i= nt *pextra_pins) > > int split_huge_page_to_list(struct page *page, struct list_head *lis= t) > > { > > struct page *head =3D compound_head(page); > > - struct pglist_data *pgdata =3D NODE_DATA(page_to_nid(head)); > > struct deferred_split *ds_queue =3D get_deferred_split_queue(head); > > struct anon_vma *anon_vma =3D NULL; > > struct address_space *mapping =3D NULL; > > int count, mapcount, extra_pins, ret; > > - unsigned long flags; > > pgoff_t end; > > =20 > > VM_BUG_ON_PAGE(is_huge_zero_page(head), head); > > @@ -2697,9 +2699,7 @@ int split_huge_page_to_list(struct page *page, = struct list_head *list) > > unmap_page(head); > > VM_BUG_ON_PAGE(compound_mapcount(head), head); > > =20 > > - /* prevent PageLRU to go away from under us, and freeze lru stats *= / > > - spin_lock_irqsave(&pgdata->lru_lock, flags); > > - > > + local_irq_disable(); > > if (mapping) { > > XA_STATE(xas, &mapping->i_pages, page_index(head)); > > =20 > > @@ -2729,7 +2729,7 @@ int split_huge_page_to_list(struct page *page, = struct list_head *list) > > __dec_node_page_state(head, NR_FILE_THPS); > > } > > =20 > > - __split_huge_page(page, list, end, flags); > > + __split_huge_page(page, list, end); > > if (PageSwapCache(head)) { > > swp_entry_t entry =3D { .val =3D page_private(head) }; > > =20 > > @@ -2748,7 +2748,7 @@ int split_huge_page_to_list(struct page *page, = struct list_head *list) > > spin_unlock(&ds_queue->split_queue_lock); > > fail: if (mapping) > > xa_unlock(&mapping->i_pages); > > - spin_unlock_irqrestore(&pgdata->lru_lock, flags); > > + local_irq_enable(); > > remap_page(head); > > ret =3D -EBUSY; > > } > >=20