From: Daeho Jeong <[email protected]> During the garbage collection process, F2FS submits readahead I/Os for valid blocks. However, since the GC loop runs within a single plug scope without intermediate flushing, these readahead I/Os often accumulate in the block layer's plug list instead of being dispatched to the device immediately.
Consequently, when the GC thread attempts to lock the page later, the I/O might not have completed (or even started), leading to a "read try and wait" scenario. This negates the benefit of readahead and causes unnecessary delays in GC latency. This patch addresses this issue by introducing an intermediate blk_finish_plug() and blk_start_plug() pair within the GC loop. This forces the dispatch of pending I/Os, ensuring that readahead pages are fetched in time, thereby reducing GC latency. Signed-off-by: Daeho Jeong <[email protected]> --- fs/f2fs/gc.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index 384fa7e2085b..8ffc3d4f7989 100644 --- a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -1031,7 +1031,8 @@ static int check_valid_map(struct f2fs_sb_info *sbi, * ignore that. */ static int gc_node_segment(struct f2fs_sb_info *sbi, - struct f2fs_summary *sum, unsigned int segno, int gc_type) + struct f2fs_summary *sum, unsigned int segno, int gc_type, + struct blk_plug *plug) { struct f2fs_summary *entry; block_t start_addr; @@ -1100,8 +1101,11 @@ static int gc_node_segment(struct f2fs_sb_info *sbi, stat_inc_node_blk_count(sbi, 1, gc_type); } - if (++phase < 3) + if (++phase < 3) { + blk_finish_plug(plug); + blk_start_plug(plug); goto next_step; + } if (fggc) atomic_dec(&sbi->wb_sync_req[NODE]); @@ -1535,7 +1539,7 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type, */ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum, struct gc_inode_list *gc_list, unsigned int segno, int gc_type, - bool force_migrate) + bool force_migrate, struct blk_plug *plug) { struct super_block *sb = sbi->sb; struct f2fs_summary *entry; @@ -1703,8 +1707,11 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum, } } - if (++phase < 5) + if (++phase < 5) { + blk_finish_plug(plug); + blk_start_plug(plug); goto next_step; + } return submitted; } @@ -1853,11 +1860,11 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi, */ if (type == SUM_TYPE_NODE) submitted += gc_node_segment(sbi, sum->entries, - cur_segno, gc_type); + cur_segno, gc_type, &plug); else submitted += gc_data_segment(sbi, sum->entries, gc_list, cur_segno, - gc_type, force_migrate); + gc_type, force_migrate, &plug); stat_inc_gc_seg_count(sbi, data_type, gc_type); sbi->gc_reclaimed_segs[sbi->gc_mode]++; -- 2.52.0.351.gbe84eed79e-goog _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
