On Tue, Jan 3, 2017 at 5:59 PM, Al Viro wrote:
> On Tue, Jan 03, 2017 at 05:38:54PM -0800, Dan Williams wrote:
>> > 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
>> > having only used movnt; it does not attempt clwb at all.
>>
>> Yes, and there was
On Tue, Jan 3, 2017 at 5:59 PM, Al Viro wrote:
> On Tue, Jan 03, 2017 at 05:38:54PM -0800, Dan Williams wrote:
>> > 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
>> > having only used movnt; it does not attempt clwb at all.
>>
>> Yes, and there was a fix a while back to
On Tue, Jan 03, 2017 at 05:38:54PM -0800, Dan Williams wrote:
> > 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
> > having only used movnt; it does not attempt clwb at all.
>
> Yes, and there was a fix a while back to make sure it always used
> movnt so clwb after the fact
On Tue, Jan 03, 2017 at 05:38:54PM -0800, Dan Williams wrote:
> > 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
> > having only used movnt; it does not attempt clwb at all.
>
> Yes, and there was a fix a while back to make sure it always used
> movnt so clwb after the fact
On Tue, Jan 3, 2017 at 3:22 PM, Al Viro wrote:
> On Tue, Jan 03, 2017 at 01:14:11PM -0800, Dan Williams wrote:
>
>> Robert was describing the overall flow / mechanics, but I think it is
>> easier to visualize the sfence as a flush command sent to a disk
>> device with a
On Tue, Jan 3, 2017 at 3:22 PM, Al Viro wrote:
> On Tue, Jan 03, 2017 at 01:14:11PM -0800, Dan Williams wrote:
>
>> Robert was describing the overall flow / mechanics, but I think it is
>> easier to visualize the sfence as a flush command sent to a disk
>> device with a volatile cache. In fact,
On Tue, Jan 3, 2017 at 3:46 PM, Linus Torvalds
wrote:
> On Tue, Jan 3, 2017 at 3:22 PM, Al Viro wrote:
>>
>> 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
>> having only used movnt; it does not attempt clwb at all.
On Tue, Jan 3, 2017 at 3:46 PM, Linus Torvalds
wrote:
> On Tue, Jan 3, 2017 at 3:22 PM, Al Viro wrote:
>>
>> 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
>> having only used movnt; it does not attempt clwb at all.
>>
>> 2) __copy_from_user_nocache() for short copies does
On Tue, Jan 3, 2017 at 3:22 PM, Al Viro wrote:
>
> 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
> having only used movnt; it does not attempt clwb at all.
>
> 2) __copy_from_user_nocache() for short copies does not use movnt at all.
> In that case
On Tue, Jan 3, 2017 at 3:22 PM, Al Viro wrote:
>
> 1) memcpy_to_pmem() seems to rely upon the __copy_from_user_nocache()
> having only used movnt; it does not attempt clwb at all.
>
> 2) __copy_from_user_nocache() for short copies does not use movnt at all.
> In that case neither sfence nor clwb
On Tue, Jan 03, 2017 at 01:14:11PM -0800, Dan Williams wrote:
> Robert was describing the overall flow / mechanics, but I think it is
> easier to visualize the sfence as a flush command sent to a disk
> device with a volatile cache. In fact, that's how we implemented it in
> the pmem block device
On Tue, Jan 03, 2017 at 01:14:11PM -0800, Dan Williams wrote:
> Robert was describing the overall flow / mechanics, but I think it is
> easier to visualize the sfence as a flush command sent to a disk
> device with a volatile cache. In fact, that's how we implemented it in
> the pmem block device
el-
>> > ow...@vger.kernel.org] On Behalf Of Al Viro
>> > Sent: Friday, December 30, 2016 8:26 PM
>> > Subject: [RFC] memcpy_nocache() and memcpy_writethrough()
>> >
>> ...
>> > Why does pmem need writethrough warranties, anyway?
>>
>> U
g] On Behalf Of Al Viro
>> > Sent: Friday, December 30, 2016 8:26 PM
>> > Subject: [RFC] memcpy_nocache() and memcpy_writethrough()
>> >
>> ...
>> > Why does pmem need writethrough warranties, anyway?
>>
>> Using either
>> * nontemporal st
:26 PM
> > Subject: [RFC] memcpy_nocache() and memcpy_writethrough()
> >
> ...
> > Why does pmem need writethrough warranties, anyway?
>
> Using either
> * nontemporal store instructions; or
> * following regular store instructions with a sequence of cache flush
:26 PM
> > Subject: [RFC] memcpy_nocache() and memcpy_writethrough()
> >
> ...
> > Why does pmem need writethrough warranties, anyway?
>
> Using either
> * nontemporal store instructions; or
> * following regular store instructions with a sequence of cache flush
> -Original Message-
> From: linux-kernel-ow...@vger.kernel.org [mailto:linux-kernel-
> ow...@vger.kernel.org] On Behalf Of Al Viro
> Sent: Friday, December 30, 2016 8:26 PM
> Subject: [RFC] memcpy_nocache() and memcpy_writethrough()
>
...
> Why does pmem need wr
> -Original Message-
> From: linux-kernel-ow...@vger.kernel.org [mailto:linux-kernel-
> ow...@vger.kernel.org] On Behalf Of Al Viro
> Sent: Friday, December 30, 2016 8:26 PM
> Subject: [RFC] memcpy_nocache() and memcpy_writethrough()
>
...
> Why does pmem need wr
On Thu, Dec 29, 2016 at 08:56:13PM -0800, Dan Williams wrote:
> > Um... Then we do have a problem - nocache variant of uaccess primitives
> > does *not* guarantee that clwb is redundant.
> >
> > What about the requirements of e.g. tcp_sendmsg() with its use of
> > skb_add_data_nocache()? What
On Thu, Dec 29, 2016 at 08:56:13PM -0800, Dan Williams wrote:
> > Um... Then we do have a problem - nocache variant of uaccess primitives
> > does *not* guarantee that clwb is redundant.
> >
> > What about the requirements of e.g. tcp_sendmsg() with its use of
> > skb_add_data_nocache()? What
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