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Date: Sat, 24 Dec 2022 19:46:39 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Sean Christopherson <seanjc@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Joerg Roedel <jroedel@...e.de>,
Ard Biesheuvel <ardb@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Tom Lendacky <thomas.lendacky@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Dario Faggioli <dfaggioli@...e.com>,
Dave Hansen <dave.hansen@...el.com>,
Mike Rapoport <rppt@...nel.org>,
David Hildenbrand <david@...hat.com>,
Mel Gorman <mgorman@...hsingularity.net>,
marcelo.cerri@...onical.com, tim.gardner@...onical.com,
khalid.elmously@...onical.com, philip.cox@...onical.com,
aarcange@...hat.com, peterx@...hat.com, x86@...nel.org,
linux-mm@...ck.org, linux-coco@...ts.linux.dev,
linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCHv8 02/14] mm: Add support for unaccepted memory
On Fri, Dec 09, 2022 at 11:23:50PM +0100, Vlastimil Babka wrote:
> On 12/9/22 20:26, Kirill A. Shutemov wrote:
> >> > #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> >> > /*
> >> > * Watermark failed for this zone, but see if we can
> >> > @@ -4299,6 +4411,9 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
> >> >
> >> > return page;
> >> > } else {
> >> > + if (try_to_accept_memory(zone))
> >> > + goto try_this_zone;
> >>
> >> On the other hand, here we failed the full rmqueue(), including the
> >> potentially fragmenting fallbacks, so I'm worried that before we finally
> >> fail all of that and resort to accepting more memory, we already fragmented
> >> the already accepted memory, more than necessary.
> >
> > I'm not sure I follow. We accept memory in pageblock chunks. Do we want to
> > allocate from a free pageblock if we have other memory to tap from? It
> > doesn't make sense to me.
>
> The fragmentation avoidance based on migratetype does work with pageblock
> granularity, so yeah, if you accept a single pageblock worth of memory and
> then (through __rmqueue_fallback()) end up serving both movable and
> unmovable allocations from it, the whole fragmentation avoidance mechanism
> is defeated and you end up with unmovable allocations (e.g. page tables)
> scattered over many pageblocks and inability to allocate any huge pages.
>
> >> So one way to prevent would be to move the acceptance into rmqueue() to
> >> happen before __rmqueue_fallback(), which I originally had in mind and maybe
> >> suggested that previously.
> >
> > I guess it should be pretty straight forward to fail __rmqueue_fallback()
> > if there's non-empty unaccepted_pages list and steer to
> > try_to_accept_memory() this way.
>
> That could be a way indeed. We do have ALLOC_NOFRAGMENT which could be
> possible to employ here.
> But maybe the zone_watermark_fast() modification would be simpler yet
> sufficient. It makes sense to me that we'd try to keep a high watermark
> worth of pre-accepted memory. zone_watermark_fast() would fail at low
> watermark, so we could try accepting (high-low) at a time instead of single
> pageblock.
Looks like we already have __zone_watermark_unusable_free() that seems
match use-case rather closely. We only need switch unaccepted memory to
per-zone accounting.
The fixup below suppose to do the trick, but I'm not sure how to test
fragmentation avoidance properly.
Any suggestions?
diff --git a/drivers/base/node.c b/drivers/base/node.c
index ca6f0590be21..1bd2d245edee 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -483,7 +483,7 @@ static ssize_t node_read_meminfo(struct device *dev,
#endif
#ifdef CONFIG_UNACCEPTED_MEMORY
,
- nid, K(node_page_state(pgdat, NR_UNACCEPTED))
+ nid, K(sum_zone_node_page_state(nid, NR_UNACCEPTED))
#endif
);
len += hugetlb_report_node_meminfo(buf, len, nid);
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 789b77c7b6df..e9c05b4c457c 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -157,7 +157,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
#ifdef CONFIG_UNACCEPTED_MEMORY
show_val_kb(m, "Unaccepted: ",
- global_node_page_state(NR_UNACCEPTED));
+ global_zone_page_state(NR_UNACCEPTED));
#endif
hugetlb_report_meminfo(m);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9c762e8175fc..8b5800cd4424 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -152,6 +152,9 @@ enum zone_stat_item {
NR_ZSPAGES, /* allocated in zsmalloc */
#endif
NR_FREE_CMA_PAGES,
+#ifdef CONFIG_UNACCEPTED_MEMORY
+ NR_UNACCEPTED,
+#endif
NR_VM_ZONE_STAT_ITEMS };
enum node_stat_item {
@@ -198,9 +201,6 @@ enum node_stat_item {
NR_FOLL_PIN_ACQUIRED, /* via: pin_user_page(), gup flag: FOLL_PIN */
NR_FOLL_PIN_RELEASED, /* pages returned via unpin_user_page() */
NR_KERNEL_STACK_KB, /* measured in KiB */
-#ifdef CONFIG_UNACCEPTED_MEMORY
- NR_UNACCEPTED,
-#endif
#if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
NR_KERNEL_SCS_KB, /* measured in KiB */
#endif
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e80e8d398863..404b267332a9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1779,7 +1779,7 @@ static bool try_to_accept_memory(struct zone *zone)
migratetype = get_pfnblock_migratetype(page, page_to_pfn(page));
__mod_zone_freepage_state(zone, -1 << order, migratetype);
- __mod_node_page_state(page_pgdat(page), NR_UNACCEPTED, -1 << order);
+ __mod_zone_page_state(zone, NR_UNACCEPTED, -1 << order);
spin_unlock_irqrestore(&zone->lock, flags);
if (last)
@@ -1808,7 +1808,7 @@ static void __free_unaccepted(struct page *page, unsigned int order)
migratetype = get_pfnblock_migratetype(page, page_to_pfn(page));
list_add_tail(&page->lru, &zone->unaccepted_pages);
__mod_zone_freepage_state(zone, 1 << order, migratetype);
- __mod_node_page_state(page_pgdat(page), NR_UNACCEPTED, 1 << order);
+ __mod_zone_page_state(zone, NR_UNACCEPTED, 1 << order);
spin_unlock_irqrestore(&zone->lock, flags);
if (first)
@@ -4074,6 +4074,9 @@ static inline long __zone_watermark_unusable_free(struct zone *z,
if (!(alloc_flags & ALLOC_CMA))
unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
#endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+ unusable_free += zone_page_state(z, NR_UNACCEPTED);
+#endif
return unusable_free;
}
--
Kiryl Shutsemau / Kirill A. Shutemov
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