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Date: Tue, 15 Jan 2013 08:30:22 +0800 From: majianpeng <majianpeng@...il.com> To: "Vivek Goyal" <vgoyal@...hat.com> Cc: axboe <axboe@...nel.dk>, linux-kernel <linux-kernel@...r.kernel.org>, tj <tj@...nel.org> Subject: Re: Re: [PATCH] blkcg: Before starting a new slice, firstly count bps/iops limit in func tg_may_dispatch. >On Mon, Jan 14, 2013 at 10:15:58AM +0800, majianpeng wrote: > >[..] >> >Index: linux-2.6/block/blk-throttle.c >> >=================================================================== >> >--- linux-2.6.orig/block/blk-throttle.c 2012-10-18 01:52:28.000000000 -0400 >> >+++ linux-2.6/block/blk-throttle.c 2013-01-14 03:40:41.355731375 -0500 >> >@@ -648,8 +648,14 @@ static bool tg_may_dispatch(struct throt >> > * If previous slice expired, start a new one otherwise renew/extend >> > * existing slice to make sure it is at least throtl_slice interval >> > * long since now. >> >+ * >> >+ * Start a new slice only if there is no bio queued in that direction. >> >+ * That bio is waiting to be dispatched and slice needs to be >> >+ * extended. It might happen that bio waited to be dispatched but >> >+ * workqueue execution got little late it might restart a new slice >> >+ * instead of taking all the waited time into account. >> > */ >> >- if (throtl_slice_used(td, tg, rw)) >> >+ if (throtl_slice_used(td, tg, rw) && !tg->nr_queued[rw]) >> > throtl_start_new_slice(td, tg, rw); >> > else { >> > if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) >> Hi vivek, >> Your patch is ok.But i had a question: >> What's condition tg->nr_queued[rw] = 0, but bio is not null? > >When a new bio is about to be queued in an empty group (look at >blk_throtl_bio). At that time, tg->nr_queued[rw] might be 0 if no other >bio is already queued. > >Thanks >Vivek I see. Thanks your time! Jianpeng Thanks!
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