hw/nvme: reenable cqe batching

Commit 2e53b0b45024 ("hw/nvme: Use ioeventfd to handle doorbell
updates") had the unintended effect of disabling batching of CQEs.

This patch changes the sq/cq timers to bottom halfs and instead of
calling nvme_post_cqes() immediately (causing an interrupt per cqe), we
defer the call.

                   | iops
  -----------------+------
    baseline       | 138k
    +cqe batching  | 233k

Fixes: 2e53b0b45024 ("hw/nvme: Use ioeventfd to handle doorbell updates")
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Jinhao Fan <fanjinhao21s@ict.ac.cn>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/hw/nvme/nvme.h b/hw/nvme/nvme.h
index 79f5c281c2..7adf042ec3 100644
--- a/hw/nvme/nvme.h
+++ b/hw/nvme/nvme.h
@@ -375,7 +375,7 @@ typedef struct NvmeSQueue {
     uint64_t    dma_addr;
     uint64_t    db_addr;
     uint64_t    ei_addr;
-    QEMUTimer   *timer;
+    QEMUBH      *bh;
     EventNotifier notifier;
     bool        ioeventfd_enabled;
     NvmeRequest *io_req;
@@ -396,7 +396,7 @@ typedef struct NvmeCQueue {
     uint64_t    dma_addr;
     uint64_t    db_addr;
     uint64_t    ei_addr;
-    QEMUTimer   *timer;
+    QEMUBH      *bh;
     EventNotifier notifier;
     bool        ioeventfd_enabled;
     QTAILQ_HEAD(, NvmeSQueue) sq_list;