From: Johannes Weiner <hannes@cmpxchg.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Shaohua Li <shli@fb.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Kernel-team@fb.com, mhocko@suse.com, hughd@google.com,
riel@redhat.com, mgorman@techsingularity.net,
akpm@linux-foundation.org
Subject: Re: [PATCH V3 3/7] mm: reclaim MADV_FREE pages
Date: Fri, 17 Feb 2017 11:15:32 -0500 [thread overview]
Message-ID: <20170217161532.GC23735@cmpxchg.org> (raw)
In-Reply-To: <20170217054108.GA3653@bbox>
On Fri, Feb 17, 2017 at 02:41:08PM +0900, Minchan Kim wrote:
> Hi Johannes,
>
> On Thu, Feb 16, 2017 at 01:40:18PM -0500, Johannes Weiner wrote:
> > On Tue, Feb 14, 2017 at 11:36:09AM -0800, Shaohua Li wrote:
> > > @@ -911,7 +911,7 @@ static void page_check_dirty_writeback(struct page *page,
> > > * Anonymous pages are not handled by flushers and must be written
> > > * from reclaim context. Do not stall reclaim based on them
> > > */
> > > - if (!page_is_file_cache(page)) {
> > > + if (!page_is_file_cache(page) || page_is_lazyfree(page)) {
> >
> > Do we need this? MADV_FREE clears the dirty bit off the page; we could
> > just let them go through with the function without any special-casing.
>
> I thought some driver potentially can do GUP with FOLL_TOUCH so that the
> lazyfree page can have PG_dirty with !PG_swapbacked. In this case,
> throttling logic of shrink_page_list can be confused?
Yep, agreed. We should filter these pages here.
> > > @@ -1142,7 +1144,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> > > * The page is mapped into the page tables of one or more
> > > * processes. Try to unmap it here.
> > > */
> > > - if (page_mapped(page) && mapping) {
> > > + if (page_mapped(page) && (mapping || lazyfree)) {
> >
> > Do we actually need to filter for mapping || lazyfree? If we fail to
> > allocate swap, we don't reach here. If the page is a truncated file
> > page, ttu returns pretty much instantly with SWAP_AGAIN. We should be
> > able to just check for page_mapped() alone, no?
>
> try_to_unmap_one assumes every anonymous pages reached will have swp_entry
> so it should be changed to check PageSwapCache if we go to the way.
Yep, I think it should check page_mapping(). To me that would make the
most sense, see other email: "Don't unmap a ram page with valid data
when there is no secondary storage mapping to maintain integrity."
next prev parent reply other threads:[~2017-02-17 16:15 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-14 19:36 [PATCH V3 0/7] mm: fix some MADV_FREE issues Shaohua Li
2017-02-14 19:36 ` [PATCH V3 1/7] mm: don't assume anonymous pages have SwapBacked flag Shaohua Li
2017-02-16 17:39 ` Johannes Weiner
2017-02-14 19:36 ` [PATCH V3 2/7] mm: move MADV_FREE pages into LRU_INACTIVE_FILE list Shaohua Li
2017-02-16 17:52 ` Johannes Weiner
2017-02-17 0:35 ` Shaohua Li
2017-02-17 16:22 ` Johannes Weiner
2017-02-14 19:36 ` [PATCH V3 3/7] mm: reclaim MADV_FREE pages Shaohua Li
2017-02-16 18:40 ` Johannes Weiner
2017-02-17 0:27 ` Shaohua Li
2017-02-17 5:45 ` Minchan Kim
2017-02-17 16:11 ` Johannes Weiner
2017-02-17 16:01 ` Johannes Weiner
2017-02-17 18:43 ` Shaohua Li
2017-02-17 20:03 ` Johannes Weiner
2017-02-17 5:41 ` Minchan Kim
2017-02-17 9:27 ` Minchan Kim
2017-02-17 16:15 ` Johannes Weiner [this message]
2017-02-14 19:36 ` [PATCH V3 4/7] mm: enable MADV_FREE for swapless system Shaohua Li
2017-02-17 16:16 ` Johannes Weiner
2017-02-14 19:36 ` [PATCH V3 5/7] mm: add vmstat account for MADV_FREE pages Shaohua Li
2017-02-14 19:36 ` [PATCH V3 6/7] proc: show MADV_FREE pages info in smaps Shaohua Li
2017-02-14 19:36 ` [PATCH V3 7/7] mm: add a separate RSS for MADV_FREE pages Shaohua Li
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