linux-kernel - Re: [PATCH v3 1/7] libsas: Use static sas event pool to appease sas event lost

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Date:   Wed, 12 Jul 2017 10:06:03 +0800
From:   wangyijing <wangyijing@...wei.com>
To:     John Garry <john.garry@...wei.com>, <jejb@...ux.vnet.ibm.com>,
        <martin.petersen@...cle.com>
CC:     <chenqilin2@...wei.com>, <hare@...e.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chenxiang66@...ilicon.com>, <huangdaode@...ilicon.com>,
        <wangkefeng.wang@...wei.com>, <zhaohongjiang@...wei.com>,
        <dingtianhong@...wei.com>, <guohanjun@...wei.com>,
        <yanaijie@...wei.com>, <hch@....de>, <dan.j.williams@...el.com>,
        <emilne@...hat.com>, <thenzl@...hat.com>, <wefu@...hat.com>,
        <charles.chenxin@...wei.com>, <chenweilong@...wei.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Linuxarm <linuxarm@...wei.com>
Subject: Re: [PATCH v3 1/7] libsas: Use static sas event pool to appease sas
 event lost

>> -    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?

There is no special meaning for the pool size, if flutter of > 25 events, notify sas events will return error, and the further step work is depending on LLDD drivers.
I hope libsas could do more work in this case, but now it seems a little difficult, this patch may be a interim fix, until we find a perfect solution.

Thanks!
Yijing.

> 
> Thanks,
> John
> 
> 
> .
>