Can I do the optimization like: if (ttm->caching_state == tt_cached) - drm_clflush_pages(ttm->pages, ttm->num_pages); + for (i = 0; i < ttm->num_pages; ++i) + if (PageHighMem(ttm->pages[i])) + drm_clflush_pages(&ttm->pages[i], 1); only do flush cache when high memory and leave the linear memory flush in function set_memory_uc/wc? <div class="gmail_quote">2012/3/20 Jerome Glisse <<a href="mailto:j.glisse@gmail.com">j.glisse@gmail.com</a>> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div></div><div class="h5">On Mon, 2012-03-19 at 23:11 +0800, Scott Fang wrote: > In function ttm_tt_set_caching > ,,,,,,, > > if (ttm->caching_state == tt_cached) > drm_clflush_pages(ttm->pages, ttm->num_pages); > > for (i = 0; i < ttm->num_pages; ++i) { > cur_page = ttm->pages[i]; > if (likely(cur_page != NULL)) { > ret = ttm_tt_set_page_caching(cur_page, > ttm->caching_state, > c_state); > if (unlikely(ret != 0)) > goto out_err; > } > } > > ttm->caching_state = c_state; > > return 0; > > > drm_clflush_pages flush cache one time. > then in the following function > ttm_tt_set_page_caching->set_memory_wc->change_page_attr_set: in this > function may flush page cache again. > > Does the code do some abundant flush, or there is some trick to these > codes? > > Thanks for the answer in advance. </div></div>Yes there might be redundant flushing. Cheers, Jerome </blockquote></div>