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Message-ID: <20051116150141.29549.qmail@web34113.mail.mud.yahoo.com>
Date: Wed, 16 Nov 2005 07:01:40 -0800 (PST)
From: Kenny Simpson <theonetruekenny@yahoo.com>
Subject: Re: mmap over nfs leads to excessive system load
To: Trond Myklebust <trond.myklebust@fys.uio.no>,
       Andrew Morton <akpm@osdl.org>
Cc: Kenny Simpson <theonetruekenny@yahoo.com>, linux-kernel@vger.kernel.org
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--- 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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