Messages in this thread | | | Subject | Re: [PATCH v3 1/7] libsas: Use static sas event pool to appease sas event lost | From | John Garry <> | Date | Tue, 11 Jul 2017 16:37:25 +0100 |
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On 10/07/2017 08:06, Yijing Wang wrote: > Now libsas hotplug work is static, every sas event type has its own > static work, LLDD driver queue the hotplug work into shost->work_q. > If LLDD driver burst post lots hotplug events to libsas, the hotplug > events may pending in the workqueue like > > shost->work_q > new work[PORTE_BYTES_DMAED] --> |[PHYE_LOSS_OF_SIGNAL][PORTE_BYTES_DMAED] -> processing > |<-------wait worker to process-------->| > In this case, a new PORTE_BYTES_DMAED event coming, libsas try to queue it > to shost->work_q, but this work is already pending, so it would be lost. > Finally, libsas delete the related sas port and sas devices, but LLDD driver > expect libsas add the sas port and devices(last sas event). > > This patch and use static sas event work pool to appease this issue, since > it's static work pool, it won't make memory exhaust. >
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> > +#define PORT_POOL_SIZE (PORT_NUM_EVENTS * 5) > +#define PHY_POOL_SIZE (PHY_NUM_EVENTS * 5) > + > /* The phy pretty much is controlled by the LLDD. > * The class only reads those fields. > */ > struct asd_sas_phy { > /* private: */ > - struct asd_sas_event port_events[PORT_NUM_EVENTS]; > - struct asd_sas_event phy_events[PHY_NUM_EVENTS]; > - > - unsigned long port_events_pending; > - unsigned long phy_events_pending; > + struct asd_sas_event port_events[PORT_POOL_SIZE]; > + struct asd_sas_event phy_events[PHY_POOL_SIZE]; > > int error;
Hi Yijing,
So now we are creating a static pool of events per PHY/port, instead of having 1 static work struct per event per PHY/port. So, for sure, this avoids the dynamic event issue of system memory exhaustion which we discussed in v1+v2 series. And it seems to possibly remove issue of losing SAS events.
But how did you determine the pool size for a PHY/port? It would seem to be 5 * #phy events or #port events (which is also 5, I figure by coincidence). How does this deal with flutter of >25 events?
Thanks, John
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