Messages in this thread | | | Date | Thu, 1 May 2014 22:05:23 -0700 | From | Christoph Hellwig <> | Subject | Re: [PATCH RFC 0/2] percpu_ida: Take into account CPU topology when stealing tags |
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On Thu, May 01, 2014 at 08:19:39PM -0600, Jens Axboe wrote: > I've taken the consequence of this and implemented another tagging > scheme that blk-mq will use if it deems that percpu_ida isn't going > to be effective for the device being initialized. But I really hate > to have both of them in there. Unfortunately I have no devices > available that have a tag space that will justify using percu_ida, > so comparisons are a bit hard at the moment. NVMe should change > that, though, so decision will have to be deferred until that is > tested.
At least for SCSI devices _tag space_ is plenty, it's just the we artifically limit our tag space to the queue depth to avoid having to track that one separately. In addition we also preallocaste a request for each tag, so even if we would track the queue depth separately we would waste a lot of memory.
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