From: Mike Rapoport <rppt@kernel.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-kernel@vger.kernel.org, Alan Cox <alan@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Christopher Lameter <cl@linux.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Idan Yaniv <idan.yaniv@ibm.com>,
James Bottomley <jejb@linux.ibm.com>,
Matthew Wilcox <willy@infradead.org>,
Peter Zijlstra <peterz@infradead.org>,
"Reshetova, Elena" <elena.reshetova@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Tycho Andersen <tycho@tycho.ws>,
linux-api@vger.kernel.org, linux-mm@kvack.org,
Mike Rapoport <rppt@linux.ibm.com>
Subject: Re: [RFC PATCH v2 4/5] mm: secretmem: use PMD-size pages to amortize direct map fragmentation
Date: Mon, 13 Jul 2020 18:32:34 +0300 [thread overview]
Message-ID: <20200713153234.GC707159@kernel.org> (raw)
In-Reply-To: <20200713110505.mesvinqjbj7imsdz@box>
On Mon, Jul 13, 2020 at 02:05:05PM +0300, Kirill A. Shutemov wrote:
> On Mon, Jul 06, 2020 at 08:20:50PM +0300, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@linux.ibm.com>
> >
> > Removing a PAGE_SIZE page from the direct map every time such page is
> > allocated for a secret memory mapping will cause severe fragmentation of
> > the direct map. This fragmentation can be reduced by using PMD-size pages
> > as a pool for small pages for secret memory mappings.
> >
> > Add a gen_pool per secretmem inode and lazily populate this pool with
> > PMD-size pages.
> >
> > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> > ---
> > mm/secretmem.c | 107 ++++++++++++++++++++++++++++++++++++++++---------
> > 1 file changed, 88 insertions(+), 19 deletions(-)
> >
> > diff --git a/mm/secretmem.c b/mm/secretmem.c
> > index df8f8c958cc2..c6fcf6d76951 100644
> > --- a/mm/secretmem.c
> > +++ b/mm/secretmem.c
> > @@ -5,6 +5,7 @@
> > #include <linux/memfd.h>
> > #include <linux/printk.h>
> > #include <linux/pagemap.h>
> > +#include <linux/genalloc.h>
> > #include <linux/pseudo_fs.h>
> > #include <linux/set_memory.h>
> > #include <linux/sched/signal.h>
> > @@ -23,24 +24,66 @@
> > #define SECRETMEM_UNCACHED 0x2
> >
> > struct secretmem_ctx {
> > + struct gen_pool *pool;
> > unsigned int mode;
> > };
> >
> > -static struct page *secretmem_alloc_page(gfp_t gfp)
> > +static int secretmem_pool_increase(struct secretmem_ctx *ctx, gfp_t gfp)
> > {
> > - /*
> > - * FIXME: use a cache of large pages to reduce the direct map
> > - * fragmentation
> > - */
> > - return alloc_page(gfp);
> > + unsigned long nr_pages = (1 << HPAGE_PMD_ORDER);
> > + struct gen_pool *pool = ctx->pool;
> > + unsigned long addr;
> > + struct page *page;
> > + int err;
> > +
> > + page = alloc_pages(gfp, HPAGE_PMD_ORDER);
> > + if (!page)
> > + return -ENOMEM;
> > +
> > + addr = (unsigned long)page_address(page);
> > + split_page(page, HPAGE_PMD_ORDER);
> > +
> > + err = gen_pool_add(pool, addr, HPAGE_PMD_SIZE, NUMA_NO_NODE);
> > + if (err) {
> > + __free_pages(page, HPAGE_PMD_ORDER);
> > + return err;
> > + }
> > +
> > + __kernel_map_pages(page, nr_pages, 0);
>
> It's worth nothing that unlike flush_tlb_kernel_range(),
> __kernel_map_pages() only flushed local TLB, so other CPU may still have
> access to the page. It's shouldn't be a blocker, but deserve a comment.
Sure.
> > +
> > + return 0;
> > +}
> > +
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-07-13 15:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 17:20 [RFC PATCH v2 0/5] mm: extend memfd with ability to create "secret" memory areas Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 1/5] mm: make HPAGE_PxD_{SHIFT,MASK,SIZE} always available Mike Rapoport
2020-07-07 5:07 ` Hugh Dickins
2020-07-07 6:47 ` Mike Rapoport
2020-07-10 16:40 ` Andrea Arcangeli
2020-07-10 16:57 ` Matthew Wilcox
2020-07-10 17:08 ` Andrea Arcangeli
2020-07-10 17:12 ` Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 2/5] mmap: make mlock_future_check() global Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 3/5] mm: extend memfd with ability to create "secret" memory areas Mike Rapoport
2020-07-13 10:58 ` Kirill A. Shutemov
2020-07-13 15:31 ` Mike Rapoport
2020-07-06 17:20 ` [RFC PATCH v2 4/5] mm: secretmem: use PMD-size pages to amortize direct map fragmentation Mike Rapoport
2020-07-13 11:05 ` Kirill A. Shutemov
2020-07-13 15:32 ` Mike Rapoport [this message]
2020-07-06 17:20 ` [RFC PATCH v2 5/5] mm: secretmem: add ability to reserve memory at boot Mike Rapoport
2020-07-17 8:36 ` [RFC PATCH v2 0/5] mm: extend memfd with ability to create "secret" memory areas Pavel Machek
2020-07-17 14:43 ` James Bottomley
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