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SubjectRe: mmap over nfs leads to excessive system load
--- Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> Anyhow, does the following patch help?

Unfortunately, not:

samples % symbol name
545009 15.2546 find_get_pages_tag
450595 12.6120 mpage_writepages
383196 10.7255 release_pages
381479 10.6775 unlock_page
351513 9.8387 clear_page_dirty_for_io
317784 8.8947 pci_conf1_write
167918 4.7000 __lookup_tag
160701 4.4980 page_waitqueue
59142 1.6554 _spin_lock_irqsave
47655 1.3338 skb_copy_bits
39136 1.0954 __wake_up_bit
38143 1.0676 _read_lock_irqsave


With reducing the window size to 32k, things aren't much different:
samples % symbol name
474589 21.2001 find_get_pages_tag
370512 16.5509 mpage_writepages
310556 13.8727 release_pages
302571 13.5160 unlock_page
286541 12.7999 clear_page_dirty_for_io
119717 5.3478 page_waitqueue
109920 4.9102 __lookup_tag
33313 1.4881 pci_conf1_write
29198 1.3043 __wake_up_bit
27075 1.2095 _read_lock_irqsave
25009 1.1172 _read_unlock_irq

... except the performance is much worse than with the 2M buffer (hence the 2M choice). With the
smaller buffer, the throughput starts at 8M/sec and quickly drops to 1M/sec.

-Kenny




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