Re: unexpected paging during large file reads in 2.1.127

[Zlatko Calusic <Zlatko.Calusic@CARNet.hr>]

OK, benchmarking done (never faster :))

Methodology: compile kernel, reboot, fire up X, XEmacs, Netscape, few
xterms to (almost) fill memory, copy 1.5GB of files to /dev/null.

I have 64MB of memory, and interesting thing, in both cases I tried,
system decided to swap out cca 16MB, which is fine. Without patching,
kernel would start thrashing very early, during file copy, which
considerably slows down whole operation (and make machine painfully
sloooow).


*** Case 1)

shrink_mmap():
        count_max = (limit<<4) >> (priority>>1);
        count_min = (limit<<4) >> (priority);

Result after copying is finished:
    3 root       7   7     0    0     0 SWN     0  0.0  0.0   0:13 kswapd
                                                              ^^^^


*** Case 2)

shrink_one_page():
        age_page(page);
        age_page(page);
        age_page(page);

Result after copying is finished:
    3 root       7   7     0    0     0 SWN     0  0.0  0.0   0:07 kswapd
                                                              ^^^^


Tested on pre-2.1.128-1.

Q.E.D. :)
-- 
Posted by Zlatko Calusic           E-mail: <Zlatko.Calusic@CARNet.hr>
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