On Fri, Feb 23, 2018 at 04:02:27PM +0800, Huang, Ying wrote:
> <minchan@xxxxxxxxxx> writes:
> [snip]
>
> > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > index 39ae7cfad90f..c56cce64b2c3 100644
> > --- a/mm/swap_state.c
> > +++ b/mm/swap_state.c
> > @@ -332,32 +332,38 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
> > unsigned long addr)
> > {
> > struct page *page;
> > - unsigned long ra_info;
> > - int win, hits, readahead;
> >
> > page = find_get_page(swap_address_space(entry), swp_offset(entry));
> >
> > INC_CACHE_INFO(find_total);
> > if (page) {
> > + bool vma_ra = swap_use_vma_readahead();
> > + bool readahead = TestClearPageReadahead(page);
> > +
>
> TestClearPageReadahead() cannot be called for compound page. As in
>
> PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
> TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
>
> > INC_CACHE_INFO(find_success);
> > if (unlikely(PageTransCompound(page)))
> > return page;
> > - readahead = TestClearPageReadahead(page);
>
> So we can only call it here after checking whether page is compound.
Hi Huang,
Thanks for cathing this.
However, I don't see the reason we should rule out THP page for
readahead marker. Could't we relax the rule?
I hope we can do so that we could remove PageTransCompound check
for readahead marker, which makes code ugly.
>From 748b084d5c3960ec2418d8c51a678aada30f1072 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@xxxxxxxxxx>
Date: Mon, 26 Feb 2018 13:46:43 +0900
Subject: [PATCH] mm: relax policy for PG_readahead
This flag is in use for anon THP page so let's relax it.
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
include/linux/page-flags.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e34a27727b9a..f12d4dfae580 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -318,8 +318,8 @@ PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
/* PG_readahead is only used for reads; PG_reclaim is only for writes */
PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
-PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
- TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
+PAGEFLAG(Readahead, reclaim, PF_NO_TAIL)
+ TESTCLEARFLAG(Readahead, reclaim, PF_NO_TAIL)
#ifdef CONFIG_HIGHMEM
/*
--
2.16.1.291.g4437f3f132-goog
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