From 569ba74a7ba69f46ce2950bf085b37fea2408385 Mon Sep 17 00:00:00 2001 From: Mark Salyzyn Date: Mon, 21 Sep 2015 21:39:50 +0100 Subject: [PATCH] arm64: readahead: fault retry breaks mmap file read random detection This is the arm64 portion of commit 45cac65b0fcd ("readahead: fault retry breaks mmap file read random detection"), which was absent from the initial port and has since gone unnoticed. The original commit says: > .fault now can retry. The retry can break state machine of .fault. In > filemap_fault, if page is miss, ra->mmap_miss is increased. In the second > try, since the page is in page cache now, ra->mmap_miss is decreased. And > these are done in one fault, so we can't detect random mmap file access. > > Add a new flag to indicate .fault is tried once. In the second try, skip > ra->mmap_miss decreasing. The filemap_fault state machine is ok with it. With this change, Mark reports that: > Random read improves by 250%, sequential read improves by 40%, and > random write by 400% to an eMMC device with dm crypto wrapped around it. Cc: Shaohua Li Cc: Rik van Riel Cc: Wu Fengguang Cc: Signed-off-by: Mark Salyzyn Signed-off-by: Riley Andrews Signed-off-by: Will Deacon --- arch/arm64/mm/fault.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index aba9ead1384c..9fadf6d7039b 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -287,6 +287,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, * starvation. */ mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; + mm_flags |= FAULT_FLAG_TRIED; goto retry; } } -- GitLab