Re: mmap()/VM problems in 2.4.0

[Zlatko Calusic <zlatko@iskon.hr>]

"Vlad Bolkhovitine" <vladb@sw.com.sg> writes:

> Here is updated info for 2.4.1pre3:
> 
> Size is MB, BlkSz is Bytes, Read, Write, and Seeks are MB/sec
> 
> with mmap()
> 
>  File   Block  Num          Seq Read    Rand Read   Seq Write  Rand Write
>  Dir    Size   Size    Thr Rate (CPU%) Rate (CPU%) Rate (CPU%) Rate (CPU%)
> ------- ------ ------- --- ----------- ----------- ----------- -----------
>    .     1024   4096    2  1.089 1.24% 0.235 0.45% 1.118 4.11% 0.616 1.41%
> 
> without mmap()
>    
>  File   Block  Num          Seq Read    Rand Read   Seq Write  Rand Write
>  Dir    Size   Size    Thr Rate (CPU%) Rate (CPU%) Rate (CPU%) Rate (CPU%)
> ------- ------ ------- --- ----------- ----------- ----------- -----------
>    .     1024   4096    2  28.41 41.0% 0.547 1.15% 13.16 16.1% 0.652 1.46%
> 
> 
> Mmap() performance dropped dramatically down to almost unusable level. Plus,
> system was unusable during test: "vmstat 1" updated results every 1-2 _MINUTES_!
> 

You need Marcelo's patch. Please apply and retest.



--- linux.orig/mm/vmscan.c      Mon Jan 15 02:33:15 2001
+++ linux/mm/vmscan.c   Mon Jan 15 02:46:25 2001
@@ -153,7 +153,7 @@

                        if (VALID_PAGE(page) && !PageReserved(page)) {
                                try_to_swap_out(mm, vma, address, pte,
page);
-                               if (--count)
+                               if (!--count)
                                        break;
                        }
                }


-- 
Zlatko
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