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bh=hld9DWzesHJspBjBdWtXXwcmpnWRtXWYimDUyNVg7lU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NCioxuAfrpjY7ec504lTvTZ+IWhdxj9/I78lN61qo3KmdYRj/MGpD7SMBgOkwepEM Nw77NzcT+Km4Y3muHT1eO2fLL+92+9kY2PiCa2UPRa7Dk9ynVw870WBY7YiGrZTv87 v2OR3+8mOB7G94py+ob8315RACYrmCH0kHdxFVaI= Date: Wed, 28 Dec 2022 15:22:06 -0800 From: Andrew Morton To: Huang Ying Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zi Yan , Yang Shi , Baolin Wang , Oscar Salvador , Matthew Wilcox , Bharata B Rao , Alistair Popple , haoxin Subject: Re: [PATCH 5/8] migrate_pages: batch _unmap and _move Message-Id: <20221228152206.52435aef4072c4cad9087541@linux-foundation.org> In-Reply-To: <20221227002859.27740-6-ying.huang@intel.com> References: <20221227002859.27740-1-ying.huang@intel.com> <20221227002859.27740-6-ying.huang@intel.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: sojm5ne8jzfwas43me6bhydtburheohi X-Rspam-User: X-Rspamd-Queue-Id: CCFFD20006 X-Rspamd-Server: rspam06 X-HE-Tag: 1672269730-222825 X-HE-Meta: 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 iWwLFerY 7z7lglVsARg3tq389IhEHqLyznpALN1C623RNdbQiBHom4dJCWKe04vve1Hun2jtcfnd/Cg6LrM6/fzA7F/tmOt1OGS1l5hFym86S701K4s3WeVHPVVOF06lELA== 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 Tue, 27 Dec 2022 08:28:56 +0800 Huang Ying wrote: > In this patch the _unmap and _move stage of the folio migration is > batched. That for, previously, it is, > > for each folio > _unmap() > _move() > > Now, it is, > > for each folio > _unmap() > for each folio > _move() > > Based on this, we can batch the TLB flushing and use some hardware > accelerator to copy folios between batched _unmap and batched _move > stages. > > ... > > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1027,8 +1027,32 @@ static void __migrate_folio_extract(struct folio *dst, > dst->private = NULL; > } > > +static void migrate_folio_undo_src(struct folio *src, > + int page_was_mapped, > + struct anon_vma *anon_vma, > + struct list_head *ret) > +{ > + if (page_was_mapped) > + remove_migration_ptes(src, src, false); > + if (anon_vma) > + put_anon_vma(anon_vma); > + folio_unlock(src); > + list_move_tail(&src->lru, ret); > +} > + > +static void migrate_folio_undo_dst(struct folio *dst, > + free_page_t put_new_page, > + unsigned long private) > +{ > + folio_unlock(dst); > + if (put_new_page) > + put_new_page(&dst->page, private); > + else > + folio_put(dst); > +} What do the above do? Are they so obvious that no comments are needed? > static int __migrate_folio_unmap(struct folio *src, struct folio *dst, > - int force, enum migrate_mode mode) > + int force, bool force_lock, enum migrate_mode mode) > { > int rc = -EAGAIN; > int page_was_mapped = 0; > @@ -1055,6 +1079,11 @@ static int __migrate_folio_unmap(struct folio *src, struct folio *dst, > if (current->flags & PF_MEMALLOC) > goto out; > > + if (!force_lock) { > + rc = -EDEADLOCK; > + goto out; > + } Please document the use of EDEADLOCK in this code. What does it signify? > folio_lock(src); > } >