Messages in this thread Patch in this message | | | Date | Sat, 16 Nov 2002 17:00:33 -0800 | From | Andrew Morton <> | Subject | Re: 2.5.47-mm3 IO rate question |
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Badari Pulavarty wrote: > > ... > max_sectors = 512 > SG_SEGMENTS = 32 > [root]# vmstat 5 > procs memory swap io system cpu > r b w swpd free buff cache si so bi bo in cs us sy id > 0 20 0 0 3652472 7752 34464 0 0 170755 15 2354 3477 2 98 0 > 0 20 0 0 3652472 7756 34464 0 0 172771 3 2363 3512 2 98 0 > 0 20 0 0 3652472 7760 34464 0 0 174031 3 2372 3576 0 100 0 > 0 20 0 0 3652408 7764 34464 0 0 173074 7 2384 3538 10 87 3 > 0 20 0 0 3652408 7768 34464 0 0 172670 3 2364 3502 2 98 0
I don't know what happened to your bandwidth, but that context switch rate is excessive. qlogic's small BIOs are hurting.
We don't actually need to perform a wakeup-per-BIO in there. It is sufficient to deliver a single wakeup on the very last BIO.
This should drop your CPU load a bit. (vmstat numbers might not change - the statistical process accounting may not be very accurate for this sort of thing. Use cyclesoak: http://www.zip.com.au/~akpm/linux/#zc)
fs/direct-io.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-)
--- 25/fs/direct-io.c~dio-reduce-context-switch-rate Sat Nov 16 16:55:25 2002 +++ 25-akpm/fs/direct-io.c Sat Nov 16 16:55:25 2002 @@ -105,7 +105,8 @@ struct dio { int page_errors; /* errno from get_user_pages() */ /* BIO completion state */ - atomic_t bio_count; /* nr bios in flight */ + atomic_t bio_count; /* nr bios to be completed */ + atomic_t bios_in_flight; /* nr bios in flight */ spinlock_t bio_list_lock; /* protects bio_list */ struct bio *bio_list; /* singly linked via bi_private */ struct task_struct *waiter; /* waiting task (NULL if none) */ @@ -238,7 +239,8 @@ static int dio_bio_end_io(struct bio *bi spin_lock_irqsave(&dio->bio_list_lock, flags); bio->bi_private = dio->bio_list; dio->bio_list = bio; - if (dio->waiter) + atomic_dec(&dio->bios_in_flight); + if (dio->waiter && atomic_read(&dio->bios_in_flight) == 0) wake_up_process(dio->waiter); spin_unlock_irqrestore(&dio->bio_list_lock, flags); return 0; @@ -271,6 +273,7 @@ static void dio_bio_submit(struct dio *d bio->bi_private = dio; atomic_inc(&dio->bio_count); + atomic_inc(&dio->bios_in_flight); submit_bio(dio->rw, bio); dio->bio = NULL; @@ -852,6 +855,7 @@ direct_io_worker(int rw, struct kiocb *i * still submittion BIOs. */ atomic_set(&dio->bio_count, 1); + atomic_set(&dio->bios_in_flight, 0); spin_lock_init(&dio->bio_list_lock); dio->bio_list = NULL; dio->waiter = NULL; _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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