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Message-ID: <97219d3b-96e1-4371-59ea-d038f37a672a@infradead.org>
Date: Thu, 9 Jul 2020 09:39:02 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Zi Yan <ziy@...dia.com>
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 7/9/20 9:34 AM, Zi Yan wrote:
> 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.
Hi,
I am trying to build x86_64.
Maybe I am just having trouble replacing the patch file.
Like I tried to say, I would prefer to see an incremental patch
to fix mmotm or linux-next.
> mm/migrate.c and added vm events will not be used
> if CONFIG_MIGRATION is unchecked. Why would they cause compilation errors?
AFAICT, the patch adds these calls:
+ 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);
+ trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
+ nr_thp_failed, nr_thp_split, mode, reason);
even when CONFIG_MIGRATION is not set, but then the THP_MIGRATIION_SUCCESS/FAIL/SPLIT
symbols are not defined.
--
~Randy
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