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Date: Wed, 2 Feb 2011 17:55:49 -0500 From: Mike Snitzer <snitzer@...hat.com> To: Tejun Heo <tj@...nel.org>, Jens Axboe <jaxboe@...ionio.com> Cc: tytso@....edu, djwong@...ibm.com, shli@...nel.org, neilb@...e.de, adilger.kernel@...ger.ca, jack@...e.cz, linux-kernel@...r.kernel.org, kmannth@...ibm.com, cmm@...ibm.com, linux-ext4@...r.kernel.org, rwheeler@...hat.com, hch@....de, josef@...hat.com, jmoyer@...hat.com, vgoyal@...hat.com Subject: [PATCH v3 1/2] block: skip elevator data initialization for flush requests Set REQ_SORTED, in the @rw_flags passed to the request allocator, for any request that may be put on IO scheduler. Skip elevator data initialization during request allocation if REQ_SORTED is not set. REQ_SORTED is not set for flush requests because they are never put on the IO scheduler. Signed-off-by: Mike Snitzer <snitzer@...hat.com> Acked-by: Vivek Goyal <vgoyal@...hat.com> --- block/blk-core.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) v3: edits to patch header and __make_request() comment Index: linux-2.6/block/blk-core.c =================================================================== --- linux-2.6.orig/block/blk-core.c +++ linux-2.6/block/blk-core.c @@ -764,7 +764,7 @@ static struct request *get_request(struc struct request_list *rl = &q->rq; struct io_context *ioc = NULL; const bool is_sync = rw_is_sync(rw_flags) != 0; - int may_queue, priv; + int may_queue, priv = 0; may_queue = elv_may_queue(q, rw_flags); if (may_queue == ELV_MQUEUE_NO) @@ -808,9 +808,14 @@ static struct request *get_request(struc rl->count[is_sync]++; rl->starved[is_sync] = 0; - priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); - if (priv) - rl->elvpriv++; + /* + * Only initialize elevator data if REQ_SORTED is set. + */ + if (rw_flags & REQ_SORTED) { + priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); + if (priv) + rl->elvpriv++; + } if (blk_queue_io_stat(q)) rw_flags |= REQ_IO_STAT; @@ -1197,6 +1202,7 @@ static int __make_request(struct request const unsigned short prio = bio_prio(bio); const bool sync = !!(bio->bi_rw & REQ_SYNC); const bool unplug = !!(bio->bi_rw & REQ_UNPLUG); + const bool flush = !!(bio->bi_rw & (REQ_FLUSH | REQ_FUA)); const unsigned long ff = bio->bi_rw & REQ_FAILFAST_MASK; int where = ELEVATOR_INSERT_SORT; int rw_flags; @@ -1210,7 +1216,7 @@ static int __make_request(struct request spin_lock_irq(q->queue_lock); - if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) { + if (flush) { where = ELEVATOR_INSERT_FLUSH; goto get_rq; } @@ -1293,6 +1299,16 @@ get_rq: rw_flags |= REQ_SYNC; /* + * Set REQ_SORTED for all requests that may be put on IO scheduler. + * The request allocator's IO scheduler initialization will be skipped + * if REQ_SORTED is not set -- elv_set_request() is avoided so that + * that the allocated request's elevator_private pointers are not + * initialized and that space can be used by flush request data. + */ + if (!flush) + rw_flags |= REQ_SORTED; + + /* * Grab a free request. This is might sleep but can not fail. * Returns with the queue unlocked. */ -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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