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Date: Thu, 9 Jul 2020 08:34:37 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Jonathan Corbet <corbet@....net>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Daniel Jordan <daniel.m.jordan@...cle.com>,
Hugh Dickins <hughd@...gle.com>,
Matthew Wilcox <willy@...radead.org>, Zi Yan <ziy@...dia.com>,
John Hubbard <jhubbard@...dia.com>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4] mm/vmstat: Add events for THP migration without split
Hi,
I have a few comments on this.
a. I reported it very early and should have been Cc-ed.
b. A patch that applies to mmotm or linux-next would have been better
than a full replacement patch.
c. I tried replacing what I believe is the correct/same patch file in mmotm
and still have build errors.
(more below)
On 7/9/20 2:39 AM, Anshuman Khandual wrote:
> ---
> Applies on 5.8-rc4.
>
> Changes in V4:
>
> - Changed THP_MIGRATION_FAILURE as THP_MIGRATION_FAIL per John
> - Dropped all conditional 'if' blocks in migrate_pages() per Andrew and John
> - Updated migration events documentation per John
> - Updated thp_nr_pages variable as nr_subpages for an expected merge conflict
> - Moved all new THP vmstat events into CONFIG_MIGRATION
> - Updated Cc list with Documentation/ and tracing related addresses
>
> Changes in V3: (https://patchwork.kernel.org/patch/11647237/)
>
> - Formatted new events documentation with 'fmt' tool per Matthew
> - Made events universally available i.e dropped ARCH_ENABLE_THP_MIGRATION
> - Added THP_MIGRATION_SPLIT
> - Updated trace_mm_migrate_pages() with THP events
> - Made THP events update normal page migration events as well
>
> Changes in V2: (https://patchwork.kernel.org/patch/11586893/)
>
> - Dropped PMD reference both from code and commit message per Matthew
> - Added documentation and updated the commit message per Daniel
>
> Changes in V1: (https://patchwork.kernel.org/patch/11564497/)
>
> - Changed function name as thp_pmd_migration_success() per John
> - Folded in a fix (https://patchwork.kernel.org/patch/11563009/) from Hugh
>
> Changes in RFC V2: (https://patchwork.kernel.org/patch/11554861/)
>
> - Decopupled and renamed VM events from their implementation per Zi and John
> - Added THP_PMD_MIGRATION_FAILURE VM event upon allocation failure and split
>
> Changes in RFC V1: (https://patchwork.kernel.org/patch/11542055/)
>
> Documentation/vm/page_migration.rst | 27 +++++++++++++++
> include/linux/vm_event_item.h | 3 ++
> include/trace/events/migrate.h | 17 ++++++++--
> mm/migrate.c | 52 ++++++++++++++++++++++++-----
> mm/vmstat.c | 3 ++
> 5 files changed, 91 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index 24fc7c3ae7d6..2e6ca53b9bbd 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -56,6 +56,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> #endif
> #ifdef CONFIG_MIGRATION
> PGMIGRATE_SUCCESS, PGMIGRATE_FAIL,
> + THP_MIGRATION_SUCCESS,
> + THP_MIGRATION_FAIL,
> + THP_MIGRATION_SPLIT,
These 3 new symbols are still only present if CONFIG_MIGRATION=y, but the build errors
are using these symbols even when CONFIG_MIGRATION is not set.
> #endif
> #ifdef CONFIG_COMPACTION
> COMPACTMIGRATE_SCANNED, COMPACTFREE_SCANNED,
> diff --git a/mm/migrate.c b/mm/migrate.c
> index f37729673558..c706e3576cfc 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1429,22 +1429,35 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> enum migrate_mode mode, int reason)
> {
> int retry = 1;
> + int thp_retry = 1;
> int nr_failed = 0;
> int nr_succeeded = 0;
> + int nr_thp_succeeded = 0;
> + int nr_thp_failed = 0;
> + int nr_thp_split = 0;
> int pass = 0;
> + bool is_thp = false;
> struct page *page;
> struct page *page2;
> int swapwrite = current->flags & PF_SWAPWRITE;
> - int rc;
> + int rc, nr_subpages;
>
> if (!swapwrite)
> current->flags |= PF_SWAPWRITE;
>
> - for(pass = 0; pass < 10 && retry; pass++) {
> + for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
> retry = 0;
> + thp_retry = 0;
>
> list_for_each_entry_safe(page, page2, from, lru) {
> retry:
> + /*
> + * THP statistics is based on the source huge page.
> + * Capture required information that might get lost
> + * during migration.
> + */
> + is_thp = PageTransHuge(page);
> + nr_subpages = hpage_nr_pages(page);
> cond_resched();
>
> if (PageHuge(page))
> @@ -1475,15 +1488,30 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> unlock_page(page);
> if (!rc) {
> list_safe_reset_next(page, page2, lru);
> + nr_thp_split++;
> goto retry;
> }
> }
> + if (is_thp) {
> + nr_thp_failed++;
> + nr_failed += nr_subpages;
> + goto out;
> + }
> nr_failed++;
> goto out;
> case -EAGAIN:
> + if (is_thp) {
> + thp_retry++;
> + break;
> + }
> retry++;
> break;
> case MIGRATEPAGE_SUCCESS:
> + if (is_thp) {
> + nr_thp_succeeded++;
> + nr_succeeded += nr_subpages;
> + break;
> + }
> nr_succeeded++;
> break;
> default:
> @@ -1493,19 +1521,27 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> * removed from migration page list and not
> * retried in the next outer loop.
> */
> + if (is_thp) {
> + nr_thp_failed++;
> + nr_failed += nr_subpages;
> + break;
> + }
> nr_failed++;
> break;
> }
> }
> }
> - nr_failed += retry;
> + nr_failed += retry + thp_retry;
> + nr_thp_failed += thp_retry;
> rc = nr_failed;
> out:
> - if (nr_succeeded)
> - count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
> - if (nr_failed)
> - count_vm_events(PGMIGRATE_FAIL, nr_failed);
> - trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
> + count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
> + count_vm_events(PGMIGRATE_FAIL, nr_failed);
> + count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
> + count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed);
> + count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
These references still cause build errors.
> + trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
> + nr_thp_failed, nr_thp_split, mode, reason);
>
> if (!swapwrite)
> current->flags &= ~PF_SWAPWRITE;
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 3fb23a21f6dd..09914a4bfee4 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1234,6 +1234,9 @@ const char * const vmstat_text[] = {
> #ifdef CONFIG_MIGRATION
> "pgmigrate_success",
> "pgmigrate_fail",
> + "thp_migration_success",
> + "thp_migration_fail",
> + "thp_migration_split",
> #endif
> #ifdef CONFIG_COMPACTION
> "compact_migrate_scanned",
>
--
~Randy
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