Messages in this thread | | | Subject | RE: [RFC] add sysfs to dynamically control blk request tag maintenance | Date | Fri, 7 Oct 2005 00:52:00 -0700 | From | "Chen, Kenneth W" <> |
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Jens Axboe wrote on Friday, October 07, 2005 12:42 AM > > It starts out with scsi_end_request being a fairly hot function in the > > execution profile, then I noticed blk_queue_start/end_tag() are being > > called but no actual consumer of using the tag. I'm trying to find a > > way to avoid making these blk_queue_start/end_tag calls. I got the > > answer > > now. The proper way is to fix it in the scsi LLDD. Scratch this patch, > > new patch to follow :-) > > Ok that makes more sense! But it's a little worrying that > blk_queue_end_tag() would show up as hot in the profile, it is actually > quite lean.
It's probably a very small number that I'm chasing with avoiding blk layer tagging. Nevertheless, any number no matter how small, is a gold mine to me :-)
Latest execution profile taken with 2.6.14-rc2 kernel with "industry standard transaction processing database workload". First column is clock ticks (a direct measure of time), 2nd column is instruction retired, and 3rd column is number of L3 misses occurred inside the function.
Symbol Clockticks Inst. Retired L3 Misses scsi_request_fn 8.12% 9.27% 11.18% Schedule 6.52% 4.93% 7.26% scsi_end_request 4.44% 3.59% 6.76% __blockdev_direct_IO 4.28% 4.38% 3.98% __make_request 3.59% 4.16% 3.47% __wake_up 2.46% 1.56% 3.33% dio_bio_end_io 2.14% 1.67% 3.18% aio_complete 2.05% 1.27% 3.56% kmem_cache_free 1.95% 1.70% 0.71% kmem_cache_alloc 1.45% 1.84% 0.45% put_page 1.42% 0.60% 1.27% follow_hugetlb_page 1.41% 0.75% 1.27% __generic_file_aio_read 1.37% 0.36% 1.68% - 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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