Re: mmap()/VM problems in 2.4.0

Zlatko Calusic (zlatko@iskon.hr)
15 Jan 2001 21:31:56 +0100


"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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