From: Song Liu <songliubraving@fb.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Matthew Wilcox <matthew.wilcox@oracle.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Kernel Team <Kernel-team@fb.com>,
William Kucharski <william.kucharski@oracle.com>
Subject: Re: [PATCH v7 2/4] uprobe: use original page when all uprobes are removed
Date: Wed, 24 Jul 2019 08:23:53 +0000 [thread overview]
Message-ID: <EA58E3BD-7EB1-4433-8F7F-1E3894F8D563@fb.com> (raw)
In-Reply-To: <20190715152513.GD1222@redhat.com>
> On Jul 15, 2019, at 8:25 AM, Oleg Nesterov <oleg@redhat.com> wrote:
>
> On 06/25, Song Liu wrote:
>>
>> This patch allows uprobe to use original page when possible (all uprobes
>> on the page are already removed).
>
> I can't review. I do not understand vm enough.
>
>> + if (!is_register) {
>> + struct page *orig_page;
>> + pgoff_t index;
>> +
>> + index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT;
>> + orig_page = find_get_page(vma->vm_file->f_inode->i_mapping,
>> + index);
>> +
>> + if (orig_page) {
>> + if (pages_identical(new_page, orig_page)) {
>
> Shouldn't we at least check PageUptodate?
For page cache, we only do ClearPageUptodate() on read failures, so
this should be really rare case. But I guess we can check anyway.
>
> and I am a bit surprised there is no simple way to unmap the old page
> in this case...
The easiest way I have found requires flush_cache_page() plus a few
mmu_notifier calls around it. I think current solution is better than
that, as it saves a page fault.
Thanks,
Song
next prev parent reply other threads:[~2019-07-24 8:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 23:53 [PATCH v7 0/4] THP aware uprobe Song Liu
2019-06-25 23:53 ` [PATCH v7 1/4] mm: move memcmp_pages() and pages_identical() Song Liu
2019-06-25 23:53 ` [PATCH v7 2/4] uprobe: use original page when all uprobes are removed Song Liu
2019-06-26 6:00 ` Srikar Dronamraju
2019-07-15 15:25 ` Oleg Nesterov
2019-07-24 8:23 ` Song Liu [this message]
2019-07-24 8:57 ` Oleg Nesterov
2019-06-25 23:53 ` [PATCH v7 3/4] mm, thp: introduce FOLL_SPLIT_PMD Song Liu
2019-06-25 23:53 ` [PATCH v7 4/4] uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT Song Liu
2019-06-26 6:00 ` Srikar Dronamraju
2019-06-27 6:31 ` Song Liu
2019-06-26 0:03 ` [PATCH v7 0/4] THP aware uprobe Song Liu
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