CFQ: delay getting cfq group at the very point we really need it
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From: Vivek Goyal on 16 Jul 2010 10:00 On Thu, Jul 15, 2010 at 09:59:20AM +0800, Gui Jianfeng wrote: > Delay searching or allocating a cfq group at the very point that > we really need it. This change would save some cycles every time > we're getting a cfq queue. > > Signed-off-by: Gui Jianfeng <guijianfeng(a)cn.fujitsu.com> > --- > block/cfq-iosched.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index eb4086f..9b0cf13 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -2820,10 +2820,8 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, > { > struct cfq_queue *cfqq, *new_cfqq = NULL; > struct cfq_io_context *cic; > - struct cfq_group *cfqg; > > retry: > - cfqg = cfq_get_cfqg(cfqd, 1); > cic = cfq_cic_lookup(cfqd, ioc); > /* cic always exists here */ > cfqq = cic_to_cfqq(cic, is_sync); > @@ -2852,6 +2850,9 @@ retry: > } > > if (cfqq) { > + struct cfq_group *cfqg; > + > + cfqg = cfq_get_cfqg(cfqd, 1); > cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); Gui, I noticed that once we have setup a cfqq and cfqg, for subequent requests we should not come into this function at all because in cfq_set_request(), cic will have pointer to cfqq. So I am not sure in what call path there is substantial saving but anyway, it should not harm moving cfq_get_cfqg() call down and call it after cfqq has been allocated. Acked-by: Vivek Goyal <vgoyal(a)redhat.com> Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |