From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <445FF2F2.6080102@yahoo.com.au> Date: Tue, 09 May 2006 11:40:02 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: Any reason for passing "tlb" to "free_pgtables()" by address? References: <445B2EBD.4020803@bull.net> <445FBD1B.6080404@free.fr> In-Reply-To: <445FBD1B.6080404@free.fr> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Zoltan Menyhart Cc: Hugh Dickins , Zoltan Menyhart , linux-mm@kvack.org List-ID: Zoltan Menyhart wrote: > Hugh Dickins wrote: > >> Personally I'd prefer not to make your change right now - it seems >> a shame to make that cosmetic change without addressing the real >> latency issue; but I've no strong feeling against your patch. > > > Could you please explain what your plans are? Long term, we would like to make the mmu_gather paths preemptible and reentrant so the latency hacks can go away, and we don't end up with awful things like a tlb flush after unmapping every 8 pages for CONFIG_PREEMPT. I posted a quick RFC a while back to implement my "gather in place" idea: http://www.ussg.iu.edu/hypermail/linux/kernel/0603.2/0499.html Hugh has a different approach, but neither is particularly urgent at this stage. In the short term, we might still like to be able to do latency breaks in free_pgtables so it would make sense to keep the code the way it is. > > How much do you think it is worth to optimize "free_pgtables()", > knowing that: > - PTE, PMD and PUD pages are freed seldom (wrt. the leaf pages) > - The number of these pages is much more less than > that of the leaf pages. Virtual address space can still be vast and sparse. Even with 32 bits, we could probably trigger high latencies here. Nick -- Send instant messages to your online friends http://au.messenger.yahoo.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org