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Trond Myklebust <trond.myklebust@fys.uio.no> wrote: > > På su , 18/01/2004 klokka 01:41, skreiv Andrew Morton: > > It would be nice to fix up the lock_kernel()s in the NFS client: SMP lock > > contention is quite high in there. > > Chuck did a study of that particular issue some 2-3 years ago, but we've > addressed all the top problems on his list since then. Do you have any > new numbers to show us? I ask because I'm not at all convinced that the > BKL adds significantly to our latencies for the moment (I've been > looking at those number in the last few days due to the readahead > problems that have already been reported). > > I am, however, quite convinced that we need new statistics on this sort > of issue. Chuck is therefore working on a set of patches to add an > "iostat"-like tool to the NFS client. Hopefully that will help settle > these questions. > Well a quick profile of `dbench 4' on a localhost mount on a P4-HT: c01445fc kmem_cache_alloc 495 6.1875 c0140d28 buffered_rmqueue 514 1.7133 c012a8b4 del_timer_sync 1043 3.7250 c013ea58 generic_file_aio_write_nolock 1316 0.4398 c011fa60 __wake_up 1472 33.4545 c0158a35 .text.lock.read_write 1541 26.1186 c012113f .text.lock.sched 2443 4.1197 c011f3f4 schedule 2782 1.8065 c0109034 default_idle 65504 1259.6923 00000000 total 91786 0.2234 Turning on spinlock inlining: c0143ec0 kmem_cache_alloc 464 6.1053 c01405c8 buffered_rmqueue 510 1.6346 c012a260 __mod_timer 540 1.7308 c012a4d4 del_timer_sync 949 3.3893 c013e378 generic_file_aio_write_nolock 1340 0.4479 c011fa1c __wake_up 1556 29.9231 c0157054 remote_llseek 1886 6.6408 c011f3a4 schedule 5158 3.3407 c0109034 default_idle 33731 648.6731 00000000 total 59918 0.1457 That's quite a lot of contention on the lock_kernel() in remote_llseek(). The context switch rate is 45000/sec, so schedule() gets a workout. I do recall seeing quite a lot of BKL contention within NFS itself running across 100bT on 4-way. That was several months ago - maybe things improved? - 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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