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Message-ID: <875y90ap5j.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Wed, 10 May 2023 10:36:24 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Zi Yan <ziy@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>, Xin Hao <xhao@...ux.alibaba.com>,
Yang Shi <shy828301@...il.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
"Oscar Salvador" <osalvador@...e.de>,
Alistair Popple <apopple@...dia.com>
Subject: Re: [PATCH 1/2] migrate_pages_batch: simplify retrying and failure
counting of large folios
Zi Yan <ziy@...dia.com> writes:
> On 8 May 2023, at 22:20, Huang Ying wrote:
>
>> After recent changes to the retrying and failure counting in
>> migrate_pages_batch(), it was found that it's unnecessary to count
>> retrying and failure for normal, large, and THP folios separately.
>> Because we don't use retrying and failure number of large folios
>> directly. So, in this patch, we simplified retrying and failure
>> counting of large folios via counting retrying and failure of normal
>> and large folios together. This results in the reduced line number.
>>
>> This is just code cleanup, no functionality changes are expected.
>>
>> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
>> Cc: Xin Hao <xhao@...ux.alibaba.com>
>> Cc: Zi Yan <ziy@...dia.com>
>> Cc: Yang Shi <shy828301@...il.com>
>> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> Cc: Oscar Salvador <osalvador@...e.de>
>> Cc: Alistair Popple <apopple@...dia.com>
>> ---
>> mm/migrate.c | 103 +++++++++++++++++----------------------------------
>> 1 file changed, 35 insertions(+), 68 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 01cac26a3127..10709aed76d3 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1614,11 +1614,9 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> int nr_pass)
>> {
>> int retry = 1;
>> - int large_retry = 1;
>> int thp_retry = 1;
>> int nr_failed = 0;
>> int nr_retry_pages = 0;
>> - int nr_large_failed = 0;
>> int pass = 0;
>> bool is_large = false;
>> bool is_thp = false;
>> @@ -1631,9 +1629,8 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> VM_WARN_ON_ONCE(mode != MIGRATE_ASYNC &&
>> !list_empty(from) && !list_is_singular(from));
>>
>> - for (pass = 0; pass < nr_pass && (retry || large_retry); pass++) {
>> + for (pass = 0; pass < nr_pass && retry; pass++) {
>> retry = 0;
>> - large_retry = 0;
>> thp_retry = 0;
>> nr_retry_pages = 0;
>>
>> @@ -1660,7 +1657,7 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> * list is processed.
>> */
>> if (!thp_migration_supported() && is_thp) {
>> - nr_large_failed++;
>> + nr_failed++;
>> stats->nr_thp_failed++;
>> if (!try_split_folio(folio, split_folios)) {
>> stats->nr_thp_split++;
>> @@ -1688,38 +1685,33 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> * When memory is low, don't bother to try to migrate
>> * other folios, move unmapped folios, then exit.
>> */
>> - if (is_large) {
>> - nr_large_failed++;
>> - stats->nr_thp_failed += is_thp;
>> - /* Large folio NUMA faulting doesn't split to retry. */
>> - if (!nosplit) {
>> - int ret = try_split_folio(folio, split_folios);
>> -
>> - if (!ret) {
>> - stats->nr_thp_split += is_thp;
>> - break;
>> - } else if (reason == MR_LONGTERM_PIN &&
>> - ret == -EAGAIN) {
>> - /*
>> - * Try again to split large folio to
>> - * mitigate the failure of longterm pinning.
>> - */
>> - large_retry++;
>> - thp_retry += is_thp;
>> - nr_retry_pages += nr_pages;
>> - /* Undo duplicated failure counting. */
>> - nr_large_failed--;
>> - stats->nr_thp_failed -= is_thp;
>> - break;
>> - }
>> + nr_failed++;
>> + stats->nr_thp_failed += is_thp;
>> + /* Large folio NUMA faulting doesn't split to retry. */
>> + if (is_large && !nosplit) {
>> + int ret = try_split_folio(folio, split_folios);
>> +
>> + if (!ret) {
>> + stats->nr_thp_split += is_thp;
>> + break;
>> + } else if (reason == MR_LONGTERM_PIN &&
>> + ret == -EAGAIN) {
>> + /*
>> + * Try again to split large folio to
>> + * mitigate the failure of longterm pinning.
>> + */
>> + retry++;
>> + thp_retry += is_thp;
>> + nr_retry_pages += nr_pages;
>> + /* Undo duplicated failure counting. */
>> + nr_failed--;
>> + stats->nr_thp_failed -= is_thp;
>> + break;
>> }
>> - } else {
>> - nr_failed++;
>> }
>>
>> stats->nr_failed_pages += nr_pages + nr_retry_pages;
>> /* nr_failed isn't updated for not used */
>> - nr_large_failed += large_retry;
>> stats->nr_thp_failed += thp_retry;
>> rc_saved = rc;
>> if (list_empty(&unmap_folios))
>> @@ -1727,12 +1719,8 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> else
>> goto move;
>> case -EAGAIN:
>> - if (is_large) {
>> - large_retry++;
>> - thp_retry += is_thp;
>> - } else {
>> - retry++;
>> - }
>> + retry++;
>> + thp_retry += is_thp;
>> nr_retry_pages += nr_pages;
>> break;
>> case MIGRATEPAGE_SUCCESS:
>> @@ -1750,20 +1738,14 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> * removed from migration folio list and not
>> * retried in the next outer loop.
>> */
>> - if (is_large) {
>> - nr_large_failed++;
>> - stats->nr_thp_failed += is_thp;
>> - } else {
>> - nr_failed++;
>> - }
>> -
>> + nr_failed++;
>> + stats->nr_thp_failed += is_thp;
>> stats->nr_failed_pages += nr_pages;
>> break;
>> }
>> }
>> }
>> nr_failed += retry;
>> - nr_large_failed += large_retry;
>> stats->nr_thp_failed += thp_retry;
>> stats->nr_failed_pages += nr_retry_pages;
>> move:
>> @@ -1771,17 +1753,15 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> try_to_unmap_flush();
>>
>> retry = 1;
>> - for (pass = 0; pass < nr_pass && (retry || large_retry); pass++) {
>> + for (pass = 0; pass < nr_pass && retry; pass++) {
>> retry = 0;
>> - large_retry = 0;
>> thp_retry = 0;
>> nr_retry_pages = 0;
>>
>> dst = list_first_entry(&dst_folios, struct folio, lru);
>> dst2 = list_next_entry(dst, lru);
>> list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
>> - is_large = folio_test_large(folio);
>> - is_thp = is_large && folio_test_pmd_mappable(folio);
>> + is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio);
>
> Should this be part of patch 2? Or maybe just merge two patches?
OK. Will merge 2 patches.
>> nr_pages = folio_nr_pages(folio);
>>
>> cond_resched();
>> @@ -1797,12 +1777,8 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> */
>> switch(rc) {
>> case -EAGAIN:
>> - if (is_large) {
>> - large_retry++;
>> - thp_retry += is_thp;
>> - } else {
>> - retry++;
>> - }
>> + retry++;
>> + thp_retry += is_thp;
>> nr_retry_pages += nr_pages;
>> break;
>> case MIGRATEPAGE_SUCCESS:
>> @@ -1810,13 +1786,8 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> stats->nr_thp_succeeded += is_thp;
>> break;
>> default:
>> - if (is_large) {
>> - nr_large_failed++;
>> - stats->nr_thp_failed += is_thp;
>> - } else {
>> - nr_failed++;
>> - }
>> -
>> + nr_failed++;
>> + stats->nr_thp_failed += is_thp;
>> stats->nr_failed_pages += nr_pages;
>> break;
>> }
>> @@ -1825,14 +1796,10 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page,
>> }
>> }
>> nr_failed += retry;
>> - nr_large_failed += large_retry;
>> stats->nr_thp_failed += thp_retry;
>> stats->nr_failed_pages += nr_retry_pages;
>>
>> - if (rc_saved)
>> - rc = rc_saved;
>> - else
>> - rc = nr_failed + nr_large_failed;
>> + rc = rc_saved ? : nr_failed;
>> out:
>> /* Cleanup remaining folios */
>> dst = list_first_entry(&dst_folios, struct folio, lru);
>> --
>> 2.39.2
>
> Otherwise LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>
Thanks!
Best Regards,
Huang, Ying
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