On Mon, May 22, 2017 at 04:43:57PM -0700, Qing Huang wrote: > > On 5/19/2017 6:05 AM, Christoph Hellwig wrote: > > On Thu, May 18, 2017 at 04:33:53PM -0700, Qing Huang wrote: > > > This change will optimize kernel memory deregistration operations. > > > __ib_umem_release() used to call set_page_dirty_lock() against every > > > writable page in its memory region. Its purpose is to keep data > > > synced between CPU and DMA device when swapping happens after mem > > > deregistration ops. Now we choose not to set page dirty bit if it's > > > already set by kernel prior to calling __ib_umem_release(). This > > > reduces memory deregistration time by half or even more when we ran > > > application simulation test program. > > As far as I can tell this code doesn't even need set_page_dirty_lock > > and could just use set_page_dirty > > It seems that set_page_dirty_lock has been used here for more than 10 years. > Don't know the original purpose. Maybe it was used to prevent races between > setting dirty bits and swapping out pages? I suspect copy & paste. Or maybe I don't actually understand the explanation of set_page_dirty vs set_page_dirty_lock enough. But I'd rather not hack around the problem. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
