From 23d0127096cb91cb6d354bdc71bd88a7bae3a1d5 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 6 Nov 2015 16:28:55 -0800 Subject: [PATCH] fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback sync_file_range(2) is documented to issue writeback only for pages that are not currently being written. After all the system call has been created for userspace to be able to issue background writeout and so waiting for in-flight IO is undesirable there. However commit ee53a891f474 ("mm: do_sync_mapping_range integrity fix") switched do_sync_mapping_range() and thus sync_file_range() to issue writeback in WB_SYNC_ALL mode since do_sync_mapping_range() was used by other code relying on WB_SYNC_ALL semantics. These days do_sync_mapping_range() went away and we can switch sync_file_range(2) back to issuing WB_SYNC_NONE writeback. That should help PostgreSQL avoid large latency spikes when flushing data in the background. Andres measured a 20% increase in transactions per second on an SSD disk. Signed-off-by: Jan Kara Reported-by: Andres Freund Tested-By: Andres Freund Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/sync.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/sync.c b/fs/sync.c index 4ec430ae2b0d..dd5d1711c7ac 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -348,7 +348,8 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes, } if (flags & SYNC_FILE_RANGE_WRITE) { - ret = filemap_fdatawrite_range(mapping, offset, endbyte); + ret = __filemap_fdatawrite_range(mapping, offset, endbyte, + WB_SYNC_NONE); if (ret < 0) goto out_put; } -- 2.20.1