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Re: [Qemu-devel] [PATCH 2/2] add some virtio-scsi trace events
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] add some virtio-scsi trace events |
Date: |
Wed, 4 Sep 2013 16:21:05 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Aug 29, 2013 at 03:37:50PM +0200, Laszlo Ersek wrote:
> +static void dump_cmd_req(const VirtIOSCSIReq *req, uint32_t cdb_size)
> +{
> + const VirtIOSCSICmdReq *cr;
> + char *cdb_hex;
> +
> + if (!trace_event_get_state(TRACE_VIRTIO_SCSI_DUMP_CMD_REQ)) {
> + return;
> + }
> + cr = req->req.cmd;
> + cdb_hex = qemu_hexstr(cr->cdb, cdb_size, NULL);
> + trace_virtio_scsi_dump_cmd_req((void *)req, cr->tag,
> + virtio_scsi_get_lun((uint8_t *)cr->lun),
> + cdb_hex);
> + g_free(cdb_hex);
There is a halfway solution to disable expensive trace events that works
across all backends (SystemTap, stderr, etc):
if (!TRACE_VIRTIO_SCSI_DUMP_CMD_REQ_ENABLED) {
return;
}
This is a compile-time constant which can be toggled with the "disable"
keyword in the ./trace-events file:
disable my_expensive_event(const char *foo) "foo %s"
See the bottom of docs/tracing.txt for full documentation on the
"disable" keyword.
Stefan
- Re: [Qemu-devel] [PATCH 2/2] add some virtio-scsi trace events,
Stefan Hajnoczi <=