Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] Redundant Writeback IO and Reclaim Degradation due to Missing Dirty Flag Clear - [Medium] Inaccurate Watermark Check due to Counter Drift --
commit c4c05c6bea6e7dbeb49a19a207e3cc6b5e0bc762 Author: Matthew Brost <[email protected]> drm/ttm/pool: back up at native page order This commit modifies the TTM pool backup process to handle compound pages at their native order instead of unconditionally splitting them into order-0 pages. It introduces a new folio backup helper to back up contiguous subpages to shmem, alongside a proactive splitting mechanism to split pages when under memory pressure. > diff --git a/drivers/gpu/drm/ttm/ttm_backup.c > b/drivers/gpu/drm/ttm/ttm_backup.c > index 81df4cb5606b4..e67921393f56c 100644 > --- a/drivers/gpu/drm/ttm/ttm_backup.c > +++ b/drivers/gpu/drm/ttm/ttm_backup.c [ ... ] > @@ -87,53 +93,66 @@ int ttm_backup_copy_page(struct file *backup, struct page > *dst, [ ... ] > + folio_mark_accessed(to_folio); > + folio_lock(to_folio); > + folio_mark_dirty(to_folio); > + > + for (j = 0; j < to_nr; j++) > + copy_highpage(folio_file_page(to_folio, idx + i + j), > + folio_page(folio, i + j)); > + > + if (writeback && !folio_mapped(to_folio)) { [Severity: High] Does this code skip clearing the dirty flag for IO before calling shmem_writeout()? The previous implementation of ttm_backup_backup_page() called folio_clear_dirty_for_io() and folio_set_reclaim() before starting the writeback. Without clearing the dirty flag first, __folio_start_writeback() will not clear the PAGECACHE_TAG_DIRTY mark. As a result, even if the content is successfully written, the folio remains marked as dirty, potentially leading to kswapd repeatedly attempting to write it out again. > + ret = shmem_writeout(to_folio, NULL, NULL); > + if (ret == AOP_WRITEPAGE_ACTIVATE) > + folio_unlock(to_folio); > + } else { > folio_unlock(to_folio); > } > > - folio_put(to_folio); > + folio_put(to_folio); > + i += to_nr; > + *nr_pages_backed = i; > + } > > - return handle; > + return ttm_backup_shmem_idx_to_handle(idx); > } > > diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c > index 278bbe7a11add..d76bfe527ac79 100644 > --- a/drivers/gpu/drm/ttm/ttm_pool.c > +++ b/drivers/gpu/drm/ttm/ttm_pool.c [ ... ] > @@ -1010,6 +1010,38 @@ void ttm_pool_drop_backed_up(struct ttm_tt *tt) > ttm_pool_free_range(NULL, tt, ttm_cached, start_page, tt->num_pages); > } > > +static bool ttm_pool_split_for_nearly_oom(struct ttm_pool *pool, > + struct page *page) > +{ > + unsigned int order = ttm_pool_page_order(pool, page); > + int nid = pool->nid; > + enum zone_type zone_type; > + > + if (!order) > + return false; > + > + if (!numa_valid_node(nid)) > + return false; > + > +#if IS_ENABLED(CONFIG_ZONE_DMA32) > + zone_type = ZONE_DMA32; > +#else > + zone_type = ZONE_NORMAL; > +#endif > + > + for (; zone_type <= ZONE_NORMAL; ++zone_type) { > + struct zone *zone = &NODE_DATA(nid)->node_zones[zone_type]; > + > + if (zone_page_state(zone, NR_FREE_PAGES) < [Severity: Medium] Can directly reading zone_page_state() miss per-CPU counter drift? The zone_page_state() function omits per-CPU deltas, and on systems with many CPUs, this error can exceed the actual watermark gaps. Using it directly rather than zone_page_state_snapshot() or higher-level watermark APIs might cause this heuristic to read artificially high free page counts, delaying the proactive split optimization under sustained memory pressure. > + low_wmark_pages(zone) / 2) { > + ttm_pool_split_for_swap(pool, page); > + return true; > + } > + } > + > + return false; > +} -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
