60 lines
2.2 KiB
Diff
60 lines
2.2 KiB
Diff
From 26fcaf58616b8cb3ce042e31c640594ea2fb5987 Mon Sep 17 00:00:00 2001
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From: "Jan Alexander Steffens (heftig)" <jan.steffens@gmail.com>
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Date: Mon, 27 Jan 2020 18:21:09 +0100
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Subject: ZEN: INTERACTIVE: Enable background reclaim of hugepages
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Use [defer+madvise] as default khugepaged defrag strategy:
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For some reason, the default strategy to respond to THP fault fallbacks
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is still just madvise, meaning stall if the program wants transparent
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hugepages, but don't trigger a background reclaim / compaction if THP
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begins to fail allocations. This creates a snowball affect where we
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still use the THP code paths, but we almost always fail once a system
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has been active and busy for a while.
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The option "defer" was created for interactive systems where THP can
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still improve performance. If we have to fallback to a regular page due
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to an allocation failure or anything else, we will trigger a background
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reclaim and compaction so future THP attempts succeed and previous
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attempts eventually have their smaller pages combined without stalling
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running applications.
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We still want madvise to stall applications that explicitely want THP,
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so defer+madvise _does_ make a ton of sense. Make it the default for
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interactive systems, especially if the kernel maintainer left
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transparent hugepages on "always".
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Reasoning and details in the original patch: https://lwn.net/Articles/711248/
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---
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init/Kconfig | 4 ++++
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mm/huge_memory.c | 4 ++++
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2 files changed, 8 insertions(+)
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--- a/init/Kconfig
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+++ b/init/Kconfig
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@@ -165,6 +165,10 @@ config ZEN_INTERACTIVE
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Default scheduler for SQ..: mq-deadline -> bfq
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Default scheduler for MQ..: none -> kyber
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+ --- Virtual Memory Subsystem ---------------------------
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+
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+ Background-reclaim hugepages...: no -> yes
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+
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config BROKEN
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bool
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--- a/mm/huge_memory.c
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+++ b/mm/huge_memory.c
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@@ -65,7 +65,11 @@ unsigned long transparent_hugepage_flags
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
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(1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
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#endif
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+#ifdef CONFIG_ZEN_INTERACTIVE
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+ (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG)|
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+#else
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(1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
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+#endif
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(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
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(1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
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