From: Matthew Wilcox <willy@infradead.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
Song Liu <songliubraving@fb.com>,
William Kucharski <william.kucharski@oracle.com>,
Johannes Weiner <jweiner@fb.com>
Subject: Re: [PATCH 3/3] mm: Allow find_get_page to be used for large pages
Date: Fri, 6 Sep 2019 08:22:33 -0700 [thread overview]
Message-ID: <20190906152230.GY29434@bombadil.infradead.org> (raw)
In-Reply-To: <20190906135215.f4qvsswrjaentvmi@box>
On Fri, Sep 06, 2019 at 04:52:15PM +0300, Kirill A. Shutemov wrote:
> On Fri, Sep 06, 2019 at 06:41:45AM -0700, Matthew Wilcox wrote:
> > On Fri, Sep 06, 2019 at 03:59:28PM +0300, Kirill A. Shutemov wrote:
> > > > + * - FGP_PMD: We're only interested in pages at PMD granularity. If there
> > > > + * is no page here (and FGP_CREATE is set), we'll create one large enough.
> > > > + * If there is a smaller page in the cache that overlaps the PMD page, we
> > > > + * return %NULL and do not attempt to create a page.
> > >
> > > Is it really the best inteface?
> > >
> > > Maybe allow user to ask bitmask of allowed orders? For THP order-0 is fine
> > > if order-9 has failed.
> >
> > That's the semantics that filemap_huge_fault() wants. If the page isn't
> > available at order-9, it needs to return VM_FAULT_FALLBACK (and the VM
> > will call into filemap_fault() to handle the regular sized fault).
>
> Ideally, we should not have division between ->fault and ->huge_fault.
> Integrating them together will give a shorter fallback loop and more
> flexible inteface here would give benefit.
>
> But I guess it's out-of-scope of the patchset.
Heh, just a little bit ... there are about 150 occurrences of
vm_operations_struct in the kernel, and I don't fancy one bit converting
them all to use ->huge_fault instead of ->fault!
next prev parent reply other threads:[~2019-09-06 15:22 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 18:23 [PATCH 0/3] Large pages in the page cache Matthew Wilcox
2019-09-05 18:23 ` [PATCH 1/3] mm: Add __page_cache_alloc_order Matthew Wilcox
2019-09-05 18:58 ` Song Liu
2019-09-05 19:02 ` Matthew Wilcox
2019-09-05 19:06 ` Song Liu
2019-09-05 18:23 ` [PATCH 2/3] mm: Allow large pages to be added to the page cache Matthew Wilcox
2019-09-05 18:28 ` Matthew Wilcox
2019-09-05 20:56 ` kbuild test robot
2019-09-06 12:09 ` Kirill A. Shutemov
2019-09-06 13:31 ` Matthew Wilcox
2019-09-05 18:23 ` [PATCH 3/3] mm: Allow find_get_page to be used for large pages Matthew Wilcox
2019-09-05 21:41 ` kbuild test robot
2019-09-05 22:04 ` kbuild test robot
2019-09-05 22:12 ` Matthew Wilcox
2019-09-09 0:42 ` [kbuild-all] " Rong Chen
2019-09-09 1:12 ` Matthew Wilcox
2019-09-06 12:59 ` Kirill A. Shutemov
2019-09-06 13:41 ` Matthew Wilcox
2019-09-06 13:52 ` Kirill A. Shutemov
2019-09-06 15:22 ` Matthew Wilcox [this message]
2019-09-06 15:59 ` [PATCH 4/3] Prepare transhuge pages properly Matthew Wilcox
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