From: Hugh Dickins <hughd@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andi Kleen <ak@linux.intel.com>,
Christoph Lameter <cl@linux.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
David Hildenbrand <david@redhat.com>,
Suren Baghdasaryan <surenb@google.com>,
Yang Shi <shy828301@gmail.com>,
Sidhartha Kumar <sidhartha.kumar@oracle.com>,
Vishal Moola <vishal.moola@gmail.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Tejun Heo <tj@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
Michal Hocko <mhocko@suse.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 07/12] mempolicy: mpol_shared_policy_init() without pseudo-vma
Date: Tue, 26 Sep 2023 14:36:25 -0700 (PDT) [thread overview]
Message-ID: <4fe84029-ad5-63cb-f2a7-3c83ea427bf1@google.com> (raw)
In-Reply-To: <ZRIOzcI78x8BmGdo@casper.infradead.org>
On Mon, 25 Sep 2023, Matthew Wilcox wrote:
> On Mon, Sep 25, 2023 at 01:29:28AM -0700, Hugh Dickins wrote:
> > + /* alloc node covering entire file; adds ref to new */
>
> This comment is confusing. sp_alloc initialises the refcount of 'n' to 1.
> Which is the same memory referred to by the name 'new' in __mpol_dup(),
> but in this function, the name "new" refers to the mempolicy called
> "old" in __mpol_dup().
No promises, but I'll see if I can make it look better in v2.
>
> > + n = sp_alloc(0, MAX_LFS_FILESIZE >> PAGE_SHIFT, new);
> > + if (n)
> > + sp_insert(sp, n);
> > put_new:
> > mpol_put(new); /* drop initial ref */
> > free_scratch:
>
> This is all a bit inefficient, really. We call mpol_new() to get a
> new mpol, then we set it up, then we dup it, then we free it. It'd
> be nice if we could donate it instead of copying it. Maybe you'll
> do something like that later.
"later" is probably the operative word. I do have an unincluded 2017
patch where I had that same realization, and wrote "I suspect that this
series of commits may be adding to an absurdity of over-mpol_dup()ing:
but that's for some other future cleanup, right now I'm just happy not
to be corrupting or leaking mpols."
Hugh
next prev parent reply other threads:[~2023-09-26 21:36 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-25 8:17 [PATCH 00/12] mempolicy: cleanups leading to NUMA mpol without vma Hugh Dickins
2023-09-25 8:21 ` [PATCH 01/12] hugetlbfs: drop shared NUMA mempolicy pretence Hugh Dickins
2023-09-25 22:09 ` Matthew Wilcox
2023-09-25 22:46 ` Andi Kleen
2023-09-26 22:26 ` Hugh Dickins
2023-09-25 8:22 ` [PATCH 02/12] kernfs: drop shared NUMA mempolicy hooks Hugh Dickins
2023-09-25 22:10 ` Matthew Wilcox
2023-09-25 8:24 ` [PATCH 03/12] mempolicy: fix migrate_pages(2) syscall return nr_failed Hugh Dickins
2023-09-25 22:22 ` Matthew Wilcox
2023-09-26 20:47 ` Hugh Dickins
2023-09-27 8:02 ` Huang, Ying
2023-09-30 4:20 ` Hugh Dickins
2023-09-25 8:25 ` [PATCH 04/12] mempolicy trivia: delete those ancient pr_debug()s Hugh Dickins
2023-09-25 22:23 ` Matthew Wilcox
2023-09-25 8:26 ` [PATCH 05/12] mempolicy trivia: slightly more consistent naming Hugh Dickins
2023-09-25 22:28 ` Matthew Wilcox
2023-09-25 8:28 ` [PATCH 06/12] mempolicy trivia: use pgoff_t in shared mempolicy tree Hugh Dickins
2023-09-25 22:31 ` Matthew Wilcox
2023-09-25 22:38 ` Matthew Wilcox
2023-09-26 21:19 ` Hugh Dickins
2023-09-25 8:29 ` [PATCH 07/12] mempolicy: mpol_shared_policy_init() without pseudo-vma Hugh Dickins
2023-09-25 22:50 ` Matthew Wilcox
2023-09-26 21:36 ` Hugh Dickins [this message]
2023-09-25 8:30 ` [PATCH 08/12] mempolicy: remove confusing MPOL_MF_LAZY dead code Hugh Dickins
2023-09-25 22:52 ` Matthew Wilcox
2023-09-25 8:32 ` [PATCH 09/12] mm: add page_rmappable_folio() wrapper Hugh Dickins
2023-09-25 22:58 ` Matthew Wilcox
2023-09-26 21:58 ` Hugh Dickins
2023-09-25 8:33 ` [PATCH 10/12] mempolicy: alloc_pages_mpol() for NUMA policy without vma Hugh Dickins
2023-09-25 8:35 ` [PATCH 11/12] mempolicy: mmap_lock is not needed while migrating folios Hugh Dickins
2023-09-25 8:36 ` [PATCH 12/12] mempolicy: migration attempt to match interleave nodes Hugh Dickins
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