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Date: Mon, 13 Nov 2017 11:58:30 -0800 From: Shaohua Li <shli@...nel.org> To: Tejun Heo <tj@...nel.org> Cc: axboe@...nel.dk, linux-kernel@...r.kernel.org, kernel-team@...com, lizefan@...wei.com, hannes@...xchg.org, cgroups@...r.kernel.org, guro@...com Subject: Re: [PATCH 7/7] blk-throtl: don't throttle the same IO multiple times On Mon, Nov 13, 2017 at 07:57:45AM -0800, Tejun Heo wrote: > Hello, > > On Mon, Nov 13, 2017 at 03:13:48AM -0800, Tejun Heo wrote: > > You're right. If we wanna take this approach, we need to keep the > > throttled flag while cloning. The clearing part is still correct tho. > > Without that, I get 1/4 bw limit enforced. Hmm... I'm not quite sure > > where that 1/4 is coming from tho. Will investigate more. > > Okay, this is because when we spiit, the split bio is the first part > which gets issued and then the orignal bio is wound forward and > requeued. So, for the splits, the original bio is the one which gets > trimmed in the front and requeued, so not clearing BIO_THROTTLED is > enough. I think we should still copy BIO_THROTTLED on clones so that > we don't get suprises w/ other bio drivers. Oh, I think there is a better solution. Not adding a new bdev is possible. We always set the BIO_THROTTLED flag after block-throttle and copy the flag in clone. In bio_set_dev, we clear the flag. This should work I think. Thanks, Shaohua
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