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Date: Thu, 9 Jul 2020 12:34:16 -0400
From: Zi Yan <ziy@...dia.com>
To: Randy Dunlap <rdunlap@...radead.org>
CC: Anshuman Khandual <anshuman.khandual@....com>,
<linux-mm@...ck.org>, 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>,
"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
On 9 Jul 2020, at 11:34, Randy Dunlap wrote:
> 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",
>>
>
Which arch are you building? I did not see any error
after applying this patch on mmotm (reverting the existing ones)
and compiling them on x86_64. I used make x86_64_defconfig and
unselected COMPACTION and MIGRATION.
mm/migrate.c and added vm events will not be used
if CONFIG_MIGRATION is unchecked. Why would they cause compilation errors?
—
Best Regards,
Yan Zi
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