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List:       linux-arm-kernel
Subject:    questions on memory management
From:       Matthias Welwarsky <mwelwarsky () web ! de>
Date:       2004-01-24 23:43:38
Message-ID: 200401250043.39015.mwelwarsky () web ! de
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Hi all,

I'm trying to grok some details of the memory management. In particular, I'm 
trying to evaluate the performance of the VM in low memory situations. From 
what I learned so far, the only thing that prevents a read-only mapped 
executable page from being discarded under memory pressure is L_PTE_YOUNG. 
But this bit has to be emulated in software. It's set on page faults, for 
example in handle_pte_fault().

However, I wonder about the efficiency of this emulation. I assume that 
handle_pte_fault() is not being constantly executed on every access, so 
L_PTE_YOUNG is not updated for program text and readonly data. Is this 
assumption correct?

If yes, what prevents code from being discarded in the first place? Those 
pages will inadvertedly end on the inactive_list once they're sufficiently 
aged, and there's no way back other than them being discarded and paged back 
on demand?

kind regards,
	matthias


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