The patch titled
Subject: mm/memory-failure: refactor log format in soft offline code
has been added to the -mm mm-unstable branch. Its filename is
mm-memory-failure-refactor-log-format-in-soft-offline-code.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-failure-refactor-log-format-in-soft-offline-code.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>
Subject: mm/memory-failure: refactor log format in soft offline code
Date: Thu, 20 Jun 2024 18:48:53 +0000
Patch series "Userspace controls soft-offline pages", v4.
Correctable memory errors are very common on servers with large amount of
memory, and are corrected by ECC, but with two pain points to users:
1. Correction usually happens on the fly and adds latency overhead
2. Not-fully-proved theory states excessive correctable memory
errors can develop into uncorrectable memory error.
Soft offline is kernel's additional solution for memory pages having
(excessive) corrected memory errors. Impacted page is migrated to healthy
page if it is in use, then the original page is discarded for any future
use.
The actual policy on whether (and when) to soft offline should be
maintained by userspace, especially in case of an 1G HugeTLB page.
Soft-offline dissolves the HugeTLB page, either in-use or free, into
chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage. If
userspace has not acknowledged such behavior, it may be surprised when
later mmap hugepages MAP_FAILED due to lack of hugepages. In case of a
transparent hugepage, it will be split into 4K pages as well; userspace
will stop enjoying the transparent performance.
In addition, discarding the entire 1G HugeTLB page only because of
corrected memory errors sounds very costly and kernel better not doing
under the hood. But today there are at least 2 such cases:
1. GHES driver sees both GHES_SEV_CORRECTED and
CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER.
2. RAS Correctable Errors Collector counts correctable errors per
PFN and when the counter for a PFN reaches threshold
In both cases, userspace has no control of the soft offline performed by
kernel's memory failure recovery.
This patch series give userspace the control of softofflining any page:
kernel only soft offlines raw page / transparent hugepage / HugeTLB
hugepage if userspace has agreed to. The interface to userspace is a new
sysctl called enable_soft_offline under /proc/sys/vm. By default
enable_soft_line is 1 to preserve existing behavior in kernel.
This patch (of 4):
Logs from soft_offline_page and soft_offline_in_use_page have different
formats than majority of the memory failure code:
"Memory failure: 0x${pfn}: ${lower_case_message}"
Convert them to the following format:
"Soft offline: 0x${pfn}: ${lower_case_message}"
No functional change in this commit.
Link: https://lkml.kernel.org/r/20240620184856.600717-1-jiaqiyan@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20240620184856.600717-2-jiaqiyan@xxxxxxxxxx
Signed-off-by: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Frank van der Linden <fvdl@xxxxxxxxxx>
Cc: Jane Chu <jane.chu@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Naoya Horiguchi <nao.horiguchi@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
--- a/mm/memory-failure.c~mm-memory-failure-refactor-log-format-in-soft-offline-code
+++ a/mm/memory-failure.c
@@ -2640,6 +2640,9 @@ unlock_mutex:
}
EXPORT_SYMBOL(unpoison_memory);
+#undef pr_fmt
+#define pr_fmt(fmt) "Soft offline: " fmt
+
static bool mf_isolate_folio(struct folio *folio, struct list_head *pagelist)
{
bool isolated = false;
@@ -2695,7 +2698,7 @@ static int soft_offline_in_use_page(stru
if (!huge && folio_test_large(folio)) {
if (try_to_split_thp_page(page, true)) {
- pr_info("soft offline: %#lx: thp split failed\n", pfn);
+ pr_info("%#lx: thp split failed\n", pfn);
return -EBUSY;
}
folio = page_folio(page);
@@ -2707,7 +2710,7 @@ static int soft_offline_in_use_page(stru
if (PageHWPoison(page)) {
folio_unlock(folio);
folio_put(folio);
- pr_info("soft offline: %#lx page already poisoned\n", pfn);
+ pr_info("%#lx page already poisoned\n", pfn);
return 0;
}
@@ -2720,7 +2723,7 @@ static int soft_offline_in_use_page(stru
folio_unlock(folio);
if (ret) {
- pr_info("soft_offline: %#lx: invalidated\n", pfn);
+ pr_info("%#lx: invalidated\n", pfn);
page_handle_poison(page, false, true);
return 0;
}
@@ -2737,13 +2740,13 @@ static int soft_offline_in_use_page(stru
if (!list_empty(&pagelist))
putback_movable_pages(&pagelist);
- pr_info("soft offline: %#lx: %s migration failed %ld, type %pGp\n",
+ pr_info("%#lx: %s migration failed %ld, type %pGp\n",
pfn, msg_page[huge], ret, &page->flags);
if (ret > 0)
ret = -EBUSY;
}
} else {
- pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %pGp\n",
+ pr_info("%#lx: %s isolation failed, page count %d, type %pGp\n",
pfn, msg_page[huge], page_count(page), &page->flags);
ret = -EBUSY;
}
@@ -2795,7 +2798,7 @@ int soft_offline_page(unsigned long pfn,
mutex_lock(&mf_mutex);
if (PageHWPoison(page)) {
- pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
+ pr_info("%#lx: page already poisoned\n", pfn);
put_ref_page(pfn, flags);
mutex_unlock(&mf_mutex);
return 0;
_
Patches currently in -mm which might be from jiaqiyan@xxxxxxxxxx are
mm-memory-failure-refactor-log-format-in-unpoison_memory.patch
mm-memory-failure-refactor-log-format-in-soft-offline-code.patch
mm-memory-failure-userspace-controls-soft-offlining-pages.patch
selftest-mm-test-enable_soft_offline-behaviors.patch
docs-mm-add-enable_soft_offline-sysctl.patch
