linux-kernel - [PATCH v4 6/6] powerpc: Don't flush caches when adding memory

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Message-Id: <20190926045419.22827-7-alastair@au1.ibm.com>
Date:   Thu, 26 Sep 2019 14:54:12 +1000
From:   "Alastair D'Silva" <alastair@....ibm.com>
To:     alastair@...ilva.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Allison Randal <allison@...utok.net>, Qian Cai <cai@....pw>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nicholas Piggin <npiggin@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 6/6] powerpc: Don't flush caches when adding memory

From: Alastair D'Silva <alastair@...ilva.org>

This operation takes a significant amount of time when hotplugging
large amounts of memory (~50 seconds with 890GB of persistent memory).

This was orignally in commit fb5924fddf9e
("powerpc/mm: Flush cache on memory hot(un)plug") to support memtrace,
but the flush on add is not needed as it is flushed on remove.

Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
---
 arch/powerpc/mm/mem.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index a2758e473d58..9afb77a8c8d5 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -142,8 +142,6 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
 		return -EFAULT;
 	}
 
-	flush_dcache_range_chunked(start, start + size, FLUSH_CHUNK_SIZE);
-
 	return __add_pages(nid, start_pfn, nr_pages, restrictions);
 }
 
-- 
2.21.0