Messages in this thread | | | Date | Sun, 14 Aug 2005 19:22:41 +0900 | From | Hiro Yoshioka <> | Subject | Re: [RFC] [PATCH] cache pollution aware __copy_from_user_ll() |
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Thanks for your comments.
On 8/14/05, Arjan van de Ven <arjan@infradead.org> wrote: > On Sun, 2005-08-14 at 18:16 +0900, Hiro Yoshioka wrote: > > Hi, > > > > The following is a patch to reduce a cache pollution > > of __copy_from_user_ll(). > > > > When I run simple iozone benchmark to find a performance bottleneck of > > the linux kernel, I found that __copy_from_user_ll() spent CPU cycle > > most and it did many cache misses. > > > however... you copy something from userspace... aren't you going to USE > it? The non-termoral versions actually throw the data out of the > cache... so while this part might be nice, you pay BIG elsewhere....
The oprofile data does not give an evidence that we pay BIG elsewhere.
For examples, the original 2.6.12.4 Top 5 cache misses are the following,
37017 63.4603 vmlinux __copy_from_user_ll 1049 1.7984 vmlinux _spin_lock_irqsave 940 1.6115 vmlinux blk_rq_map_sg 896 1.5361 vmlinux generic_file_buffered_write 885 1.5172 vmlinux _spin_lock pattern9-0-cpu4-0-08141702
cache aware version Top 5 cache misses are 899 5.7305 vmlinux blk_rq_map_sg 569 3.6270 vmlinux journal_commit_transaction 531 3.3848 vmlinux radix_tree_delete 514 3.2764 vmlinux journal_add_journal_head 505 3.2190 vmlinux release_pages ... 89 0.5673 vmlinux _mmx_memcpy_nt pattern9-0-cpu4-0-08141625
What do you think?
Regards, Hiro - 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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