From: "Huang, Ying" <ying.huang@intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Peter Xu <peterx@redhat.com>, Hugh Dickins <hughd@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@surriel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Michal Hocko <mhocko@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Tim Chen <tim.c.chen@intel.com>
Subject: Re: [PATCH] mm: move idle swap cache pages to the tail of LRU after COW
Date: Wed, 19 May 2021 12:49:47 +0800 [thread overview]
Message-ID: <878s4b9vkk.fsf@yhuang6-desk1.ccr.corp.intel.com> (raw)
In-Reply-To: <CAHk-=wgUMC03e1Ost6q4gb7+2jWO=vBHW63OYaOHOHvi39esng@mail.gmail.com> (Linus Torvalds's message of "Tue, 18 May 2021 17:25:50 -1000")
Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Tue, May 18, 2021 at 5:17 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> This looks sensible to me (and numbers talk!), but as Rik says, it
>> would probably be a good idea to move the trylock_page()/unlock_page()
>> into try_to_free_idle_swapcache(), and that would make the calling
>> side a whole lot cleaner and easier to read.
>
> To keep the error handling simple, and keep that "if that didn't work,
> just return" logic in you had, doing it as two functions like:
>
> static inline void locked_try_to_free_idle_swapcache(struct page *page)
> { .. your current try_to_free_idle_swapcache() .. }
>
> void try_to_free_idle_swapcache(struct page *page)
> {
> if (trylock_page(page)) {
> locked_try_to_free_idle_swapcache(page);
> unlock_page(page);
> }
> }
>
> would keep that readability and simplicity.
>
> And then the wp_page_copy() code ends up being
>
> if (page_copied && PageSwapCache(old_page) && !page_mapped(old_page))
> try_to_free_idle_swapcache(old_page);
>
> which looks pretty sensible to me: if we copied the page, and the old
> page is a no longer mapped swap cache page, let's try to free it.
>
> That's still a hell of a long conditional, partly because of those
> long names. But at least it's conceptually fairly straightforward and
> easy to understand what's going on.
Thanks! That looks much better. I will do that in the next version.
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2021-05-19 4:49 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 1:33 [PATCH] mm: move idle swap cache pages to the tail of LRU after COW Huang Ying
2021-05-19 2:12 ` Rik van Riel
2021-05-19 4:56 ` Huang, Ying
2021-05-19 3:17 ` Linus Torvalds
2021-05-19 3:25 ` Linus Torvalds
2021-05-19 4:49 ` Huang, Ying [this message]
2021-05-19 14:49 ` Johannes Weiner
2021-05-20 1:22 ` Huang, Ying
2021-05-20 1:46 ` Johannes Weiner
2021-05-20 1:59 ` Huang, Ying
2021-05-20 17:49 ` Johannes Weiner
2021-05-21 2:05 ` Huang, Ying
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