Messages in this thread | | | Date | Wed, 1 Mar 2023 11:08:26 +0800 | Subject | Re: [PATCH 3/3] migrate_pages: try migrate in batch asynchronously firstly | From | Baolin Wang <> |
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On 2/24/2023 10:11 PM, Huang Ying wrote: > When we have locked more than one folios, we cannot wait the lock or > bit (e.g., page lock, buffer head lock, writeback bit) synchronously. > Otherwise deadlock may be triggered. This make it hard to batch the > synchronous migration directly. > > This patch re-enables batching synchronous migration via trying to > migrate in batch asynchronously firstly. And any folios that are > failed to be migrated asynchronously will be migrated synchronously > one by one. > > Test shows that this can restore the TLB flushing batching performance > for synchronous migration effectively. > > Signed-off-by: "Huang, Ying" <ying.huang@intel.com> > Cc: Hugh Dickins <hughd@google.com> > Cc: "Xu, Pengfei" <pengfei.xu@intel.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Stefan Roesch <shr@devkernel.io> > Cc: Tejun Heo <tj@kernel.org> > Cc: Xin Hao <xhao@linux.alibaba.com> > Cc: Zi Yan <ziy@nvidia.com> > Cc: Yang Shi <shy828301@gmail.com> > Cc: Baolin Wang <baolin.wang@linux.alibaba.com> > Cc: Matthew Wilcox <willy@infradead.org> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > --- > mm/migrate.c | 65 ++++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 55 insertions(+), 10 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 91198b487e49..c17ce5ee8d92 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1843,6 +1843,51 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page, > return rc; > } > > +static int migrate_pages_sync(struct list_head *from, new_page_t get_new_page, > + free_page_t put_new_page, unsigned long private, > + enum migrate_mode mode, int reason, struct list_head *ret_folios, > + struct list_head *split_folios, struct migrate_pages_stats *stats) > +{ > + int rc, nr_failed = 0; > + LIST_HEAD(folios); > + struct migrate_pages_stats astats; > + > + memset(&astats, 0, sizeof(astats)); > + /* Try to migrate in batch with MIGRATE_ASYNC mode firstly */ > + rc = migrate_pages_batch(from, get_new_page, put_new_page, private, MIGRATE_ASYNC, > + reason, &folios, split_folios, &astats, > + NR_MAX_MIGRATE_PAGES_RETRY); > + stats->nr_succeeded += astats.nr_succeeded; > + stats->nr_thp_succeeded += astats.nr_thp_succeeded; > + stats->nr_thp_split += astats.nr_thp_split; > + if (rc < 0) { > + stats->nr_failed_pages += astats.nr_failed_pages; > + stats->nr_thp_failed += astats.nr_thp_failed; > + list_splice_tail(&folios, ret_folios); > + return rc; > + } > + stats->nr_thp_failed += astats.nr_thp_split; > + nr_failed += astats.nr_thp_split; > + /* > + * Fall back to migrate all failed folios one by one synchronously. All > + * failed folios except split THPs will be retried, so their failure > + * isn't counted > + */ > + list_splice_tail_init(&folios, from); > + while (!list_empty(from)) { > + list_move(from->next, &folios); > + rc = migrate_pages_batch(&folios, get_new_page, put_new_page, > + private, mode, reason, ret_folios, > + split_folios, stats, NR_MAX_MIGRATE_PAGES_RETRY); > + list_splice_tail_init(&folios, ret_folios); > + if (rc < 0) > + return rc; > + nr_failed += rc; > + } > + > + return nr_failed; > +} > + > /* > * migrate_pages - migrate the folios specified in a list, to the free folios > * supplied as the target for the page migration > @@ -1874,7 +1919,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > enum migrate_mode mode, int reason, unsigned int *ret_succeeded) > { > int rc, rc_gather; > - int nr_pages, batch; > + int nr_pages; > struct folio *folio, *folio2; > LIST_HEAD(folios); > LIST_HEAD(ret_folios); > @@ -1890,10 +1935,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > if (rc_gather < 0) > goto out; > > - if (mode == MIGRATE_ASYNC) > - batch = NR_MAX_BATCHED_MIGRATION; > - else > - batch = 1; > again: > nr_pages = 0; > list_for_each_entry_safe(folio, folio2, from, lru) { > @@ -1904,16 +1945,20 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > } > > nr_pages += folio_nr_pages(folio); > - if (nr_pages >= batch) > + if (nr_pages >= NR_MAX_BATCHED_MIGRATION) > break; > } > - if (nr_pages >= batch) > + if (nr_pages >= NR_MAX_BATCHED_MIGRATION) > list_cut_before(&folios, from, &folio2->lru); > else > list_splice_init(from, &folios); > - rc = migrate_pages_batch(&folios, get_new_page, put_new_page, private, > - mode, reason, &ret_folios, &split_folios, &stats, > - NR_MAX_MIGRATE_PAGES_RETRY); > + if (mode == MIGRATE_ASYNC) > + rc = migrate_pages_batch(&folios, get_new_page, put_new_page, private, > + mode, reason, &ret_folios, &split_folios, &stats, > + NR_MAX_MIGRATE_PAGES_RETRY); > + else > + rc = migrate_pages_sync(&folios, get_new_page, put_new_page, private, > + mode, reason, &ret_folios, &split_folios, &stats);
For split folios, it seems also reasonable to use migrate_pages_sync() instead of always using fixed MIGRATE_ASYNC mode?
> list_splice_tail_init(&folios, &ret_folios); > if (rc < 0) { > rc_gather = rc;
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