Re: [PATCH 3/5] blk-mq: fix plugging in blk_sq_make_request

From: Jeff Moyer
Date: Fri May 01 2015 - 13:48:12 EST


Christoph Hellwig <hch@xxxxxx> writes:

>> - if (use_plug && !blk_queue_nomerges(q) &&
>> + if (likely(!is_flush_fua) && !blk_queue_nomerges(q) &&
>
> Please don't sprinkle likely annotations for no go reason. Especially
> on metadata write heavy workloads (e.g. an NFS server) it might be very
> likely.

I have no problem getting rid of the likely, but I was mimicing the mq
case:

blk_mq_make_request:
if (unlikely(is_flush_fua)) {
blk_mq_bio_to_request(rq, bio);
blk_insert_flush(rq);
goto run_queue;
}

So would you also want that unlikely removed?

Cheers,
Jeff
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