On 04/25/2018 09:35 AM, Eric Dumazet wrote:
>
>
> On 04/25/2018 09:22 AM, Andy Lutomirski wrote:
>
>> In general, I suspect that the zerocopy receive mechanism will only
>> really be a win in single-threaded applications that consume large
>> amounts of receive bandwidth on a single TCP socket
On 04/25/2018 09:22 AM, Andy Lutomirski wrote:
> In general, I suspect that the zerocopy receive mechanism will only
> really be a win in single-threaded applications that consume large
> amounts of receive bandwidth on a single TCP socket using lots of
> memory and don't do all that much else.
On Wed, Apr 25, 2018 at 09:20:55AM -0700, Eric Dumazet wrote:
> On 04/25/2018 09:04 AM, Matthew Wilcox wrote:
> > If you don't zap the page range, any of the CPUs in the system where
> > any thread in this task have ever run may have a TLB entry pointing to
> > this page ... if the page is being re
On 04/25/2018 09:04 AM, Matthew Wilcox wrote:
> If you don't zap the page range, any of the CPUs in the system where
> any thread in this task have ever run may have a TLB entry pointing to
> this page ... if the page is being recycled into the page allocator,
> then that page might end up as a
On Wed, Apr 25, 2018 at 9:04 AM, Matthew Wilcox wrote:
> On Wed, Apr 25, 2018 at 06:01:02AM -0700, Eric Dumazet wrote:
>> On 04/24/2018 11:28 PM, Christoph Hellwig wrote:
>> > On Tue, Apr 24, 2018 at 10:27:21PM -0700, Eric Dumazet wrote:
>> >> When adding tcp mmap() implementation, I forgot that s
On Wed, Apr 25, 2018 at 06:01:02AM -0700, Eric Dumazet wrote:
> On 04/24/2018 11:28 PM, Christoph Hellwig wrote:
> > On Tue, Apr 24, 2018 at 10:27:21PM -0700, Eric Dumazet wrote:
> >> When adding tcp mmap() implementation, I forgot that socket lock
> >> had to be taken before current->mm->mmap_sem.
On Wed, Apr 25, 2018 at 06:01:02AM -0700, Eric Dumazet wrote:
> Thanks Christoph
>
> Note the high cost of zap_page_range(), needed to avoid -EBUSY being returned
> from vm_insert_page() the second time TCP_ZEROCOPY_RECEIVE is used on one VMA.
>
> Ideally a vm_replace_page() would avoid this cost
On 04/24/2018 10:27 PM, Eric Dumazet wrote:
> When adding tcp mmap() implementation, I forgot that socket lock
> had to be taken before current->mm->mmap_sem. syzbot eventually caught
> the bug.
> +
...
> + down_read(¤t->mm->mmap_sem);
> +
> + ret = -EINVAL;
> + vma = find_vma(c
On 04/24/2018 11:28 PM, Christoph Hellwig wrote:
> On Tue, Apr 24, 2018 at 10:27:21PM -0700, Eric Dumazet wrote:
>> When adding tcp mmap() implementation, I forgot that socket lock
>> had to be taken before current->mm->mmap_sem. syzbot eventually caught
>> the bug.
>>
>> Since we can not lock th
On Tue, Apr 24, 2018 at 10:27:21PM -0700, Eric Dumazet wrote:
> When adding tcp mmap() implementation, I forgot that socket lock
> had to be taken before current->mm->mmap_sem. syzbot eventually caught
> the bug.
>
> Since we can not lock the socket in tcp mmap() handler we have to
> split the ope
When adding tcp mmap() implementation, I forgot that socket lock
had to be taken before current->mm->mmap_sem. syzbot eventually caught
the bug.
Since we can not lock the socket in tcp mmap() handler we have to
split the operation in two phases.
1) mmap() on a tcp socket simply reserves VMA space
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