Re: [PATCH 5/5] dax: always use _copy_mc_to_iter in dax_copy_to_iter

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Dec 8, 2021 at 10:38 PM Christoph Hellwig <hch@xxxxxx> wrote:
>
> While using the MC-safe copy routines is rather pointless on a virtual device
> like virtiofs, it also isn't harmful at all.  So just use _copy_mc_to_iter
> unconditionally to simplify the code.

>From a correctness perspective, yes, but from a performance perspective, see:

enable_copy_mc_fragile()

...on those platforms fast-string copy implementation is replaced with
a manual unrolled copy. So this will cause a performance regression on
those platforms.

How about let's keep this as is / still only use it for PMEM where end
users are already dealing with the performance difference across
platforms? I considered exporting an indicator of which backend
routine has been selected from arch/x86/lib/copy_mc.c, but it got
messy quickly so I fell back to just keeping the status quo.



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux