| Message ID | 20190530112811.3066-1-pbonzini@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | scsi: add support for request batching | expand |
On Thu, May 30, 2019 at 01:28:09PM +0200, Paolo Bonzini wrote: > This allows a list of requests to be issued, with the LLD only writing > the hardware doorbell when necessary, after the last request was prepared. > This is more efficient if we have lists of requests to issue, particularly > on virtualized hardware, where writing the doorbell is more expensive than > on real hardware. > > This applies to any HBA, either singlequeue or multiqueue; the second > patch implements it for virtio-scsi. > > Paolo > > Paolo Bonzini (2): > scsi_host: add support for request batching > virtio_scsi: implement request batching > > drivers/scsi/scsi_lib.c | 37 ++++++++++++++++++++++--- > drivers/scsi/virtio_scsi.c | 55 +++++++++++++++++++++++++++----------- > include/scsi/scsi_cmnd.h | 1 + > include/scsi/scsi_host.h | 16 +++++++++-- > 4 files changed, 89 insertions(+), 20 deletions(-) > > -- > 2.21.0 > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
On 30/05/19 13:28, Paolo Bonzini wrote: > This allows a list of requests to be issued, with the LLD only writing > the hardware doorbell when necessary, after the last request was prepared. > This is more efficient if we have lists of requests to issue, particularly > on virtualized hardware, where writing the doorbell is more expensive than > on real hardware. > > This applies to any HBA, either singlequeue or multiqueue; the second > patch implements it for virtio-scsi. > > Paolo > > Paolo Bonzini (2): > scsi_host: add support for request batching > virtio_scsi: implement request batching > > drivers/scsi/scsi_lib.c | 37 ++++++++++++++++++++++--- > drivers/scsi/virtio_scsi.c | 55 +++++++++++++++++++++++++++----------- > include/scsi/scsi_cmnd.h | 1 + > include/scsi/scsi_host.h | 16 +++++++++-- > 4 files changed, 89 insertions(+), 20 deletions(-) > Ping? Are there any more objections? Paolo
On 2019-06-26 9:51 a.m., Paolo Bonzini wrote: > On 30/05/19 13:28, Paolo Bonzini wrote: >> This allows a list of requests to be issued, with the LLD only writing >> the hardware doorbell when necessary, after the last request was prepared. >> This is more efficient if we have lists of requests to issue, particularly >> on virtualized hardware, where writing the doorbell is more expensive than >> on real hardware. >> >> This applies to any HBA, either singlequeue or multiqueue; the second >> patch implements it for virtio-scsi. >> >> Paolo >> >> Paolo Bonzini (2): >> scsi_host: add support for request batching >> virtio_scsi: implement request batching >> >> drivers/scsi/scsi_lib.c | 37 ++++++++++++++++++++++--- >> drivers/scsi/virtio_scsi.c | 55 +++++++++++++++++++++++++++----------- >> include/scsi/scsi_cmnd.h | 1 + >> include/scsi/scsi_host.h | 16 +++++++++-- >> 4 files changed, 89 insertions(+), 20 deletions(-) >> > > > Ping? Are there any more objections? I have no objections, just a few questions. To implement this is the scsi_debug driver, a per device queue would need to be added, correct? Then a 'commit_rqs' call would be expected at some later point and it would drain that queue and submit each command. Or is the queue draining ongoing in the LLD and 'commit_rqs' means: don't return until that queue is empty? So does that mean in the normal (i.e. non request batching) case there are two calls to the LLD for each submitted command? Or is 'commit_rqs' optional, a sync-ing type command? Doug Gilbert
On 26/06/19 16:14, Douglas Gilbert wrote: > > I have no objections, just a few questions. > > To implement this is the scsi_debug driver, a per device queue would > need to be added, correct? Yes, queuecommand would then return before calling schedule_resp (for all requests except the one with SCMD_LAST, see later). schedule_resp would then be called for all requests in a batch. > Then a 'commit_rqs' call would be expected > at some later point and it would drain that queue and submit each > command. Or is the queue draining ongoing in the LLD and 'commit_rqs' > means: don't return until that queue is empty? commit_rqs means the former; it is asynchronous. However, commit_rqs is only called if a request batch fails submission in the middle of the batch, so the request batch must be sent to the HBA. If the whole request batch is sent successfully, then the LLD takes care of sending the batch to the HBA when it sees SCMD_LAST in the request. So, in the scsi_debug case schedule_resp would be called for the whole batch from commit_rqs *and* when queuecommand sees a command with the SCMD_LAST flag set. This is exactly to avoid having two calls to the LLD in the case of no request batching. > So does that mean in the normal (i.e. non request batching) case > there are two calls to the LLD for each submitted command? Or is > 'commit_rqs' optional, a sync-ing type command? It's not syncing. It's mandatory if the queuecommand function observes SCMD_LAST, not needed at all if queuecommand ignores it. So it's not needed at all until your driver adds support for batched submission of requests to the HBA. (All this is documented by the patches in the comments for struct scsi_host_template, if those are not clear please reply to patch 1 with your doubts). Paolo
Paolo,
> Ping? Are there any more objections?
It's a core change so we'll need some more reviews. I suggest you
resubmit.
On 27/06/19 05:37, Martin K. Petersen wrote: >> Ping? Are there any more objections? > It's a core change so we'll need some more reviews. I suggest you > resubmit. Resubmit exactly the same patches? Paolo
On 6/27/19 10:17 AM, Paolo Bonzini wrote: > On 27/06/19 05:37, Martin K. Petersen wrote: >>> Ping? Are there any more objections? >> It's a core change so we'll need some more reviews. I suggest you >> resubmit. > > Resubmit exactly the same patches? > Where is the ->commit_rqs() callback invoked? I don't seem to be able to find it... Cheers, Hannes
On 05/07/19 09:13, Hannes Reinecke wrote: > On 6/27/19 10:17 AM, Paolo Bonzini wrote: >> On 27/06/19 05:37, Martin K. Petersen wrote: >>>> Ping? Are there any more objections? >>> It's a core change so we'll need some more reviews. I suggest you >>> resubmit. >> Resubmit exactly the same patches? >> Where is the ->commit_rqs() callback invoked? > I don't seem to be able to find it... Stefan answered, and the series now has three reviews! It may be late for 5.3 but I hope this can go in soon. Thanks, Paolo
Paolo, > Stefan answered, and the series now has three reviews! It may be late > for 5.3 but I hope this can go in soon. I queued these up for 5.4. Thanks!