On (25/01/28 14:29), Sergey Senozhatsky wrote: > Maybe copy-in is just an okay thing to do. Let me try to measure. Naaah, not really okay. On our memory-pressure test (4GB device, 4 CPUs) that kmap_local thingy appears to save approx 6GB of memcpy(). CPY stats: 734954 1102903168 4926116 6566654656 There were 734954 cases when we memcpy() [object spans two pages] with accumulated size of 1102903168 bytes, and 4926116 cases when we took a shortcut via kmap_local and avoided memcpy(), with accumulated size of 6566654656 bytes. In both cases I counted only RO direction for map, and WO direction for unmap.
