From d4755e15386c38e4ae532ace5acc29fbfaee42e7 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 7 Mar 2023 09:47:20 -0700 Subject: [PATCH] io_uring: avoid hashing O_DIRECT writes if the filesystem doesn't need it io_uring hashes writes to a given file/inode so that it can serialize them. This is useful if the file system needs exclusive access to the file to perform the write, as otherwise we end up with a ton of io-wq threads trying to lock the inode at the same time. This can cause excessive system time. But if the file system has flagged that it supports parallel O_DIRECT writes, then there's no need to serialize the writes. Check for that through FMODE_DIO_PARALLEL_WRITE and don't hash it if we don't need to. In a basic test of 8 threads writing to a file on XFS on a gen2 Optane, with each thread writing in 4k chunks, it improves performance from ~1350K IOPS (or ~5290MiB/sec) to ~1410K IOPS (or ~5500MiB/sec). Reviewed-by: Darrick J. Wong Signed-off-by: Jens Axboe --- io_uring/io_uring.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 722624b..1ed96ca 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -425,7 +425,13 @@ static void io_prep_async_work(struct io_kiocb *req) req->flags |= io_file_get_flags(req->file) << REQ_F_SUPPORT_NOWAIT_BIT; if (req->flags & REQ_F_ISREG) { - if (def->hash_reg_file || (ctx->flags & IORING_SETUP_IOPOLL)) + bool should_hash = def->hash_reg_file; + + /* don't serialize this request if the fs doesn't need it */ + if (should_hash && (req->file->f_flags & O_DIRECT) && + (req->file->f_mode & FMODE_DIO_PARALLEL_WRITE)) + should_hash = false; + if (should_hash || (ctx->flags & IORING_SETUP_IOPOLL)) io_wq_hash_work(&req->work, file_inode(req->file)); } else if (!req->file || !S_ISBLK(file_inode(req->file)->i_mode)) { if (def->unbound_nonreg_file) -- 2.7.4